It seems that AA does have the practice of limiting ticket sales at certain smaller airports. I recall this because I need to do an in-person ticket recently by exchanging some VDB vouchers. To avoid a trip to LAX, I was looking at other local options and was curiously reviewing each of them.
As an example, the Santa Barbara (SBA) airport info shows:
Ticket counter
Main Terminal
Daily: 4:30 a.m. – 6:30 p.m.
Future ticketing: 9 a.m. – 11 a.m.