There was a thread here the other day about a 321 with a fuel tank that was inoperative that made a fuel stop in STL on BOS-LAX instead of cancelling the flight. That plane was N990AU operating AA167 on June 11, so not the same plane, but perhaps something similar?

Even the 2001-build former US A321s can do longer flights such as PHL-SFO (2,521 miles) westbound without much trouble even with winter jet streams. US waited to get the A321-200 with that range, rather than start out with the shorter range -100, so they could replace 757s on transcons. In spite of the info in Sabre and what the captain said, I have to think this was maintenance related. If it was a fuel tank out of service, the captain may not have wanted to announce that. But I have never, ever had a fuel stop eastbound from the West Coast on an A321.