If I understand correctly, you are still looking at small rooms as if they were large ones, where 20% wall coverage has the same effect no matter where that 20% is located.
My gods we are being so literal. I'm saying that if best acoustic principles call for 20% absorption on a wall surface near the speakers, whether those panels EXACTLY cover a reflection point which works for exactly one seated position is irrelevant.
You can be off that singular, zero size point by a couple of feet and it will still sound good.
Conversly, ONLY covering that zero area point with a 1'x1' panel will be negligible.