This is a good question, and I've wondered this too.

I've checked this link - http://www.cwsi.net/aa.htm - which details the various AA fare codes in the hope of understanding which economy fares fall into which category, but I'm still none the wiser.

All my previous AA connections have been booked as part of a longer itinerary, with the TATL element booked in WTP or CW, and I've always received 20 TPs for the short AA hops. But more recently I've needed to book some standalone trips on AA and I'm unsure how many points they'll earn - would be useful to know how the AA fare codes translate across.