That sounds about right in terms of size - they aren't deleted because the majority of PostgreSQL users are using it for enterprise database applications and they either rotate the logs to backup or read through them and delete them at certain intervals.
This isn't the logging that's turned on in PT3 - this logging is turned on in the postgresql.conf file - if you set logging_collector off, save that file, then restart your PostgreSQL server, those logs won't be generated anymore.