This seems like one of those efficiency-vs-resilience problems. Sure, it's "more efficient" (in cost) to use the same empty/fill process for every plane, but when nobody can leave, some extra capacity to unload planes would help.
(i.e. Unloading to tarmac, buses)
O’Hare is under construction. They’re building an entire new terminal and are operating with a lot less spare capacity while that happens.
You don't have to go to a gate to deplane and this is an extremely rare event. They'll just pull up a staircase and have them deplane to a shuttle eventually.