As mentioned up thread, AA696 was operated by N539UW; an A321-200 built in 2009. The current configuration is C16 Y171.
B6 748 was operated by N989JT; an A321-200 built in 2017. The current configuration is C16 Y143.
The AA plane has the capacity to carry 28 additional passengers. If both planes were full, one would expect the AA bird to have less range than the B6 bird. Clearly, this route is a stretch for the AA config of this plane in certain conditions. In the event of adverse conditions, this necessitates a fuel stop. Thus the AA captain's comment about having to offload 30 pax to make the flight without a stop, sounds entirely reasonable to me.