file does not fully recognize ISO images

[halogen2]

Environment:

Xubuntu 18.04

$ lsb_release -rd
Description: Ubuntu Bionic Beaver (development branch)
Release: 18.04

$ apt-cache policy file
file:
  Installed: 1:5.32-2
  Candidate: 1:5.32-2
  Version table:
 *** 1:5.32-2 500
        500 http://us.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        100 /var/lib/dpkg/status

Steps-to-reproduce:

1) Download Xubuntu 16.04 ISO from http://cdimages.ubuntu.com/xubuntu/releases/16.04/release/xubuntu-16.04-desktop-amd64.iso

2) run: file --mime-type xubuntu-16.04-desktop-amd64.iso

3) run: file xubuntu-16.04-desktop-amd64.iso

Expected results:

Result of (2) should be:
$ file --mime-type xubuntu-16.04-desktop-amd64.iso
xubuntu-16.04-desktop-amd64.iso: application/x-iso9660-image

... and result of (3) should be:
$ file xubuntu-16.04-desktop-amd64.iso
xubuntu-16.04-desktop-amd64.iso: DOS/MBR boot sector ISO 9660 CD-ROM filesystem data (DOS/MBR boot sector) 'Xubuntu 16.04 LTS amd64' (bootable); partition 2 : ID=0xef, start-CHS (0x3ff,254,63), end-CHS (0x3ff,254,63), startsector 2410708, 4736 sectors

Actual results:

$ file --mime-type xubuntu-16.04-desktop-amd64.iso
xubuntu-16.04-desktop-amd64.iso: application/octet-stream

$ file xubuntu-16.04-desktop-amd64.iso
xubuntu-16.04-desktop-amd64.iso: DOS/MBR boot sector; partition 2 : ID=0xef, start-CHS (0x3ff,254,63), end-CHS (0x3ff,254,63), startsector 2410708, 4736 sectors

ubuntuforums thread: https://ubuntuforums.org/showthread.php?t=2388736

[halogen2 (halogen2)]

Tagging as a regression - the expected results in the description were obtained on xenial.

[halogen2 (halogen2)]

This is fixed in 22.04. Thanks!