Hi,
It's an AA operated PDX-PHX-SAN flight, same routing out and back.
I know that the OW membership requirements include business agreements with each member airline for earning and redemption; but to your point, Alaska may opt to limit AA awards on international routings only.
I rarely, if ever, see AA availability on the PDX-LAX directs on Alaska, but they are often available with Avios through BA/IB.