We got the same information when we asked... once the AP Preview days are done, reservations are no longer needed. They seemed to indicated May 17 as the magic date.
They further said whatever time you have left on your pass from the closing date (I think March 14) will be activated on your first visit after May 17. In other words, If the park closed on March 14, and your pass was supposed to expire on April 14 of last year, then whenever you next visit the park will be when your last month on the pass will start. So if you didn't go back again until, say October, then that's when your last remaining month on the pass will start. You do have to activate your pass by no later than December 2021.