You've sent me down a bit of a rabbit hole on this one, and I've spent the past two mornings reading almost all of Blish's introductions on the way to work (this morning I made it through the author's note for
Star Trek 11). They make for interesting bits of context from the period, but
@Daddy Todd is right — Blish's comments in
Star Trek 3 are only about his attempts to reconcile the two versions of "The City on the Edge of Forever."
In
Star Trek 4 he makes similar comments about "The Menagerie" and his decision to adapt the original pilot version rather than the two-parter script. But other than that, he mostly writes about the volume of fan mail (too much for him to respond to).