Ive been kind of presuming that the betas' input is taken before the book goes through proofreads and copyedits, yes ? It;s amazing the things that can sneak in there; particularly for publishers who are part of larger conglomerates who assign proofreaders globally and can easily give a piece of fiction in an unusual voice a copyeditor who thinks everything should read like a New York Times editorial... trainwreck ensues.
Correct. Sort of the first line of defense.
And agreed on the one-standard nonsense in major corporate editing; one thing that having a tight group of informal readers is that they've come to KNOW the tones, styles and other esoterica employed by the author for particular purposes, and everything read gets critiqued in that light. "Would X really say that?" is not an unusual commentary.
... but again, Jim's Johnny-on-the-spot about most mechanical aspects of his writing, so it's not a COMMON commentary.