I thought it was just for Covid. They added a team to the playoffs back when they thought that it was likely that some teams would play less than the full 16 games.
I believe the "new" playoff format was decided on awhile ago, before any of us heard about COVID19. The players union had to be involved to change any game scheduling; especially since the league is adding two additional games to the yearly schedule.
I believe the 14-team format is here to stay, regardless of C19.