witthuus, a very valid suggestion. I was going to HUCA but I had publicly tweeted Qatar airways about this and they responded saying to DM them the flight details to see if they could assign seats.
And I can't believe I forgot this on the phone with the agent, but I did this without a problem just a few months ago. I booked a roundtrip Qsuites flight, scheduled for last month (cancelled for COVID-19 of course), and had called and, over the phone, selected my seats for that flight immediately after bookingwithout any problems! On the exact same route and also with AA miles. I was so flustered by the agent yesterday I just blanked, and we went around for several minutes as I explained the ridiculousness of what he was saying. He also outright refused to let me speak to a supervisor, so that was fun.
Good idea with the QR PNR, Basanez, I think that's what I used last time actually when I selected my seats.