People who have attempted to install PGDG versions of PostgreSQL on recent Ubuntu releases have run into the cascading problem of postgresql wanting to destroy Ubuntu.
Based on the packaging: postgresql depends on postgresql-common postgresql-common breaks logrotate (>3.8) ubuntu-standard depends on logrotate profit?...
It appears the reason for the claimed breakage is a very slight update to logrotate that requires one to tell logrotate about files/directories with non-"standard" ownership/permissions. Getting logrotate to stop complaining is trivially resolved by the user by adding a single "su" directive to the /etc/logrotate.d/postgresql-common or by having PostgreSQL log to syslog.
It seems that "breaks" is overkill and the hassle imposed by that declaration far exceeds any benefit therefrom
The apt repository only really provides packages for LTS versions - it just usually happens to work on other releases as well. I believe the concern here is not to risk breaking things for the LTS users - we don't want to change the logging defaults in a minor patch upgrade.
That said, hopefully it'll get fixed at least by the next release, since that's going to be another LTS. There's been talk about changing the way the logging is done in the debian packages in general, that might also be part of the solution.