Strange port in pg_upgrade output

Hi

I was doing a test upgrade from 9.5 to 9.6 and the following lines caught my eye

postgres 10967 10911 0 15:59 pts/0 00:00:00 /usr/pgsql-9.6/bin/pg_upgrade -d /var/lib/pgsql/9.5/data -D /var/lib/pgsql/9.6/data -b /usr/pgsql-9.5/bin -B /usr/pgsql-9.6/bin -k -v
postgres 11141 1 0 16:00 pts/0 00:00:00 /usr/pgsql-9.6/bin/postgres -D /var/lib/pgsql/9.6/data -p 50432 -b -c synchronous_commit=off -c fsync=off -c full_page_writes=off -c listen_addresses= -c unix_socket_permissions=0700 -c unix_so
postgres 11160 10967 0 16:00 pts/0 00:00:00 sh -c "/usr/pgsql-9.6/bin/pg_restore" --host '/var/lib/pgsql' --port 50432 --username 'postgres' --exit-on-error --verbose --dbname 'dbname=birstdb' "pg_upgrade_dump_25288.custom" >> "pg_upgrad
postgres 11161 11160 6 16:00 pts/0 00:00:00 /usr/pgsql-9.6/bin/pg_restore --host /var/lib/pgsql --port 50432 --username postgres --exit-on-error --verbose --dbname dbname=birstdb pg_upgrade_dump_25288.custom

sudo grep -i port /var/lib/pgsql/9.6/data/postgresql.conf
[sudo] password for armandp:
port = 5432 # (change requires restart)
# supported by the operating system:

Is it something that I missed or is it intentionally using a non default port to avoid unintended client connections ?

Thanks
Armand