If they wait until after departure to release seats, there will be empty seats in FC and grumpy Medallions in the back. Bottom-line, you are never going to make everyone happy. I was auto-protected a few months ago and made it in time to claim my original flight/seat. It is not the case (as some have asserted here), that when you are auto-protected your original seat is immediately released.
I don't think anyone said that when you are protected that your original seat is immediately released, that would be rebooking not protecting. What happened to me and others were that sometime between being protected and arriving at the gate our original reservations were cancelled. The culprit seems to be the automatic rebooking system.
I think you misunderstood what I was advocating. The automatic system should be inhibited if you have been protected. In that case you have already had an input into your choice and the auto system shouldn't change that. If you are protected your reservation should not be cancelled until boarding is complete on the original flight. If there are standbys then your reservation would be cancelled after the last boarding call when standbys are are given the unclaimed seats including any upgrades. If there are no standbys (not likely for FC), the reservation could be cancelled after the flight departs when the GA has more time and it wouldn't interfere with closing the aircraft. I should have given more detail in my original post so that it would have been easier to understand.
This is no different than today when a FC passenger does online check-in and then no shows. After the final boarding call, and maybe a call with the person's name, the reservation is cancelled and a standby is upgraded.