Everything that involves an AA codeshare is weird with fare classes, and as mentioned AS does not fly that route.
For example, the same flight, AA6062/AS4770 SAN-LAX on 28Jun:
AA6062 - J5 R5 D5 I5 Y7 B7 H7 K7 M7 L7 G7 V7 S7 N7 Q7 O7 E0
AS4770 - F7 P0 I7 Y7 S7 B7 M7 H7 Q7 L7 V7 K7 G7 T7 R7
How AS is selling F7 when there's only J5 and in fact if you look at the seat map, only 5 F seats not yet assigned, is beyond me. I wouldn't think a partner would oversell the operating airline's flight.