What does Debian have to do with update-motd? As far as I know Debian does not do anything particularly funky with the motd. On my Debian testing computer it is a symlink to /var/run/motd which is a static file generated at boot.
This specific instance of pointless complexity seems to be almost only the work of of Ubuntu.
The parent is probably using this as an excuse to rail on things like the auto-generated config files that can't be edited directly (e.g. the grub/grub2 config files).
This specific instance of pointless complexity seems to be almost only the work of of Ubuntu.