Comment 4 for bug 1663725

> Are all of those included in the initramfs as well? (check with e.g. lsinitramfs)

No; but they don't need to be; it's purely helpful symlinks to provide a "name" for a device that's independent of the disk (/dev/disk/by-dname/database -> /dev/vdc).

drwxr-xr-x 2 root root 0 Mar 28 14:24 lib/udev/rules.d
-rw-r--r-- 1 root root 4250 Nov 14 01:05 lib/udev/rules.d/69-lvm-metad.rules
-rw-r--r-- 1 root root 2710 Dec 17 00:54 lib/udev/rules.d/71-seat.rules
-rw-r--r-- 1 root root 5832 Dec 17 00:54 lib/udev/rules.d/60-persistent-storage.rules
-rw-r--r-- 1 root root 961 Dec 17 00:54 lib/udev/rules.d/73-special-net-names.rules
-rw-r--r-- 1 root root 3310 Dec 17 00:54 lib/udev/rules.d/50-udev-default.rules
-rw-r--r-- 1 root root 1051 Jun 26 2015 lib/udev/rules.d/69-bcache.rules
-rw-r--r-- 1 root root 452 Dec 17 00:54 lib/udev/rules.d/75-net-description.rules
-rw-r--r-- 1 root root 2130 Mar 28 14:24 lib/udev/rules.d/63-md-raid-arrays.rules
-rw-r--r-- 1 root root 618 Dec 17 00:54 lib/udev/rules.d/80-drivers.rules
-rw-r--r-- 1 root root 210 Dec 17 00:54 lib/udev/rules.d/50-firmware.rules
-rw-r--r-- 1 root root 456 Dec 17 00:54 lib/udev/rules.d/61-persistent-storage-android.rules
-rw-r--r-- 1 root root 2446 Nov 14 01:05 lib/udev/rules.d/56-lvm.rules
-rw-r--r-- 1 root root 6919 Nov 14 01:05 lib/udev/rules.d/55-dm.rules
-rw-r--r-- 1 root root 1495 Nov 14 01:05 lib/udev/rules.d/60-persistent-storage-dm.rules
-rw-r--r-- 1 root root 692 Dec 17 00:54 lib/udev/rules.d/73-usb-net-by-mac.rules
-rw-r--r-- 1 root root 292 Dec 17 00:54 lib/udev/rules.d/80-net-setup-link.rules
-rw-r--r-- 1 root root 1366 Mar 28 14:24 lib/udev/rules.d/64-md-raid-assembly.rules

> The md-name and md-uuid symlinks are generated by the udev rules shipped by the mdadm package.

Correct; which is why it appears to be a bug in mdadm; that package provides the rules file.