Has anyone booked SEA to Santiago, Chile (SCL) or Buenos Aires, Argentina (EZE) paid tickets via alaskaair.com? Or do we have to accept the lower EQMs from booking on a partner airline website?

I have a family member looking to purchase Premium Economy SEA-SCL/EZE r/t but no tickets in any class show up on Alaska's website even when testing a wide variety of dates. Can be flexible on the destination airport between SCL and EZE, as they will be joining a tour later via local travel. I did find some tickets to GRU via AS.com on AA metal, but no Premium Economy and they aren't planning to go to Brazil so it would be an unnecessary detour.