I cannot argue with that, but:

1 - I am going to live in that room, so, using what I know from experience and reading, (I agree that theoretically the thirds theory is ideal, but fifths is not a bad alternative), plus the uses I have for the room, I choose the location of speakers, seat, furniture, and tweaks, meaning curtains, rugs, screens, whatever, then I fine tune by ear...

2 - About computer calculated results, unfortunatelly they dont work every time, for everybody, I used TMREQ room equalization to obtain flat response in my room, but no one liked the sound, me, the wife or my friends, so I went back to good old "lumpy"...