We definitely do not have to call for permission to leave the airport
When you are done, you are done, ck the computer and go home
If your friend is accepting add-ons, he has ignored very explicit guidance from APA, which was widely published and much spoken about during the 117/RSV implementation and negotiations last year, and he is being taken advantage of.
"If you let them do it to you..."
The requirement is to check for the next day's assignment, whether a flight or a RAP (short call period duty period), or nothing (Long Call... )