When using MAAS 2.5.3, and composing a machine on a pod, it creates an alias for the first interface.

The command used to compose the VM:

maas root pod compose 9 cores=2 memory=1024 interfaces='eth0:space=oam-space;eth1:space=maas2'
Success.                                                                              
Machine-readable output follows:                                                                                   {                                                                                 
    "system_id": "ar68rw",                              
    "resource_uri": "/MAAS/api/2.0/machines/ar68rw/"                                  
}

When inspecting the interfaces for this machine after:
maas root interfaces read ar68rw
Success.
Machine-readable output follows:
[
    {
        "system_id": "ar68rw",
        "parents": [],
        "effective_mtu": 1500,
        "id": 55,
        "name": "eth0",
        "type": "physical",
        "vlan": {
            "vid": 1,
            "mtu": 1500,
            "dhcp_on": true,
            "external_dhcp": null,
            "relay_vlan": null,
            "id": 5001,
            "name": "untagged",
            "primary_rack": "k87hss",
            "fabric": "default",
            "fabric_id": 1,
            "space": "oam-space",
            "secondary_rack": null,
            "resource_uri": "/MAAS/api/2.0/vlans/5001/"
        },
        "tags": [],
        "discovered": [                                                                                            
            {
                "subnet": {
                    "name": "oam",
                    "vlan": {
                        "vid": 1,
                        "mtu": 1500,
                        "dhcp_on": true,
                        "external_dhcp": null,
                        "relay_vlan": null,
                        "id": 5001,
                        "name": "untagged",
                        "primary_rack": "k87hss",
                        "fabric": "default",
                        "fabric_id": 1,
                        "space": "oam-space",
                        "secondary_rack": null,
                        "resource_uri": "/MAAS/api/2.0/vlans/5001/"
                    },
                    "cidr": "192.168.105.0/24",
                    "rdns_mode": 2,
                    "gateway_ip": "192.168.105.1",
                    "dns_servers": [],
                    "allow_dns": true,
                    "allow_proxy": true,
                    "active_discovery": false,
                    "managed": true,
                    "id": 1,
                    "space": "oam-space",
                    "resource_uri": "/MAAS/api/2.0/subnets/1/"
                },
                "ip_address": "192.168.105.14"
            }
        ],
        "vendor": null,
        "enabled": true,
        "mac_address": "52:54:00:6a:e2:ff",
        "params": "",
        "links": [
            {
                "id": 276,
                "mode": "auto",
                "subnet": {
                    "name": "oam",
                    "vlan": {
                        "vid": 1,
                        "mtu": 1500,
                        "dhcp_on": true,
                        "external_dhcp": null,
                        "relay_vlan": null,
                        "id": 5001,
                        "name": "untagged",
                        "primary_rack": "k87hss",
                        "fabric": "default",
                        "fabric_id": 1,
                        "space": "oam-space",
                        "secondary_rack": null,
                        "resource_uri": "/MAAS/api/2.0/vlans/5001/"
                    },
                    "cidr": "192.168.105.0/24",
                    "rdns_mode": 2,
                    "gateway_ip": "192.168.105.1",
                    "dns_servers": [],
                    "allow_dns": true,
                    "allow_proxy": true,
                    "active_discovery": false,
                    "managed": true,
                    "id": 1,
                    "space": "oam-space",
                    "resource_uri": "/MAAS/api/2.0/subnets/1/"
                }
            },
            {
                "id": 277,
                "mode": "auto",
                "subnet": {
                    "name": "oam",
                    "vlan": {
                        "vid": 1,
                        "mtu": 1500,
                        "dhcp_on": true,
                        "external_dhcp": null,
                        "relay_vlan": null,
                        "id": 5001,
                        "name": "untagged",
                        "primary_rack": "k87hss",
                        "fabric": "default",
                        "fabric_id": 1,
                        "space": "oam-space",
                        "secondary_rack": null,
                        "resource_uri": "/MAAS/api/2.0/vlans/5001/"
                    },
                    "cidr": "192.168.105.0/24",
                    "rdns_mode": 2,
                    "gateway_ip": "192.168.105.1",
                    "dns_servers": [],
                    "allow_dns": true,
                    "allow_proxy": true,
                    "active_discovery": false,
                    "managed": true,
                    "id": 1,
                    "space": "oam-space",
                    "resource_uri": "/MAAS/api/2.0/subnets/1/"
                }
            }
        ],
        "children": [],
        "firmware_version": null,
        "product": null,
        "resource_uri": "/MAAS/api/2.0/nodes/ar68rw/interfaces/55/"
    },
    {
        "system_id": "ar68rw",
        "parents": [],
        "effective_mtu": 1500,
        "id": 56,
        "name": "eth1",
        "type": "physical",
        "vlan": {
            "vid": 2,
            "mtu": 1500,
            "dhcp_on": false,
            "external_dhcp": null,
            "relay_vlan": null,
            "id": 5004,
            "name": "maas2",
            "primary_rack": null,
            "fabric": "default",
            "fabric_id": 1,
            "space": "maas2",
            "secondary_rack": null,
            "resource_uri": "/MAAS/api/2.0/vlans/5004/"
        },
        "tags": [],
        "discovered": null,
        "vendor": null,
        "enabled": true,
        "mac_address": "52:54:00:83:ed:00",
        "params": "",
        "links": [
            {
                "id": 278,
                "mode": "link_up"
            }
        ],
        "children": [],
        "firmware_version": null,
        "product": null,
        "resource_uri": "/MAAS/api/2.0/nodes/ar68rw/interfaces/56/"
    }
]