I have to disagree with you on row 21. Seatguru does say it's a nice seat but cautions about the immovable armrests which makes the width of the seat somewhat less than other economy seats. It is still the best seat for legroom on a 767, unless you can talk your way into row 17. Notice the half green (good seat) and half yellow (caution). It does not say it's a bad seat at any point.

I will agree with row 20 assesment. It does suck and I'm not sure why AA would make it a premium row.