Yeah, but OP was on a connection, so they'd certainly try to wait until close to T-10, especially when they know that OP just landed. It's not a no-show, it's a misconnect at that point...
I would not be sure about that at all. UA will certainly offload misconnects as no shows at T-15/30 (and downgrade as well) if it faces an oversell of the aircraft or a cabin.