I have a boarding pass stub right here in my hot little hands with a gate number on it. The only instance where BP's don't have gate numbers that I've seen is flights going to PHX or LAS. It has been widely known among regular flyers that HP changes gates constantly at it's hubs. In fact departure gates often don't show on the monitor until45 mins to an hour prior to departure.
It is one of a list of many issues that do not excite me about the current situation.
Sounds like AA at DFW.