This is a policy requirement from CSO.
Recently Francois noted that there was an interference by a firewall when trying to set up a printer. He reported that to pureos/dev Element channel and the preference was stated by the CSO that the two processes listening on 0.0.0.0 get switched to localhost.
A recent test of a fresh VM install of PureOS 10 (pureos-10~devel-gnome-oem-20220302_amd64.iso) shows these processes on 0.0.0.0
root@Virtual-Byzantium:/home/jeremiah# netstat -tulpn | grep LISTEN tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 711/cupsd tcp 0 0 127.0.0.1:4101 0.0.0.0:* LISTEN 582/brltty tcp6 0 0 ::1:631 :::* LISTEN 711/cupsd tcp6 0 0 ::1:4101 :::* LISTEN 582/brltty