I was actually wondering a similar thing. Because Delta says that you earn 1:1 on Delta purchases with the Reserve card, shouldn’t a ticket for your companion qualify there? It’s very confusingly written. It seems as though Delta purchases earn MQD at a better rate than the 20:1/10:1 ratio of regular purchases, so it isn’t clear how this earn would work.

That being said, I assume those who have predicted that companion flights would not count are probably correct. But it could certainly be clarified.