True, but with REQ I can get FR 20-130 Hz +/-2 to 3 dB, not that it necessarily sounds better better than +/- 6 dB, but I like good looking curves.
Having a nicer room response is good as long as the sound quality is not worsened.
If the response looks better on paper, but sounds worse in reality, then that's bad.
I think it's easy enough to figure out if any Room EQ improves the sound. Just apply the auto REQ and compare the same songs with REQ vs Bypass/Through mode. Then choose the one that sounds best. But it is subjective. Some people may think the sound is improved, and some people don't.
With Audyssey, ARC, DIRAC, I didn't think that REQ improved the sound, but they didn't screw up the sound either.
With YPAO (did it twice),I personally thought that REQ was actually worse than THROUGH mode.
But again, sound quality can be subjective. Some people may think YPAO improves the sound. I've even heard some people say they think YPAO sounds better than Audyssey.