Actually, as has been posted in other threads, the required check-in time does not change in this case. People (myself included) have lost seats on delayed flights for not being available (and this applies to check-in as well), the requisite time before the original departure. I think it should change, but it seems that it does not.
Cheers.
That was my thought as well, based on reading FT.\
I don't think it was a connection since the flight was DEN to DFW. Not sure who would make an AA connection in DEN.