Going from a product of selective breeding to a product of genetic engineering is a pretty big rewrite.
Yeah, like... anyone... noticed that.
Like I stated before, if you were able to show me that any of these fished for in hindsight complaints about TWOK showed up in at least one review at the time of TWOK's release, I consider accepting it as legitimate argument. But until that, I state that nobody even noticed that and that it wasn't an issue at all. Nobody went out of TWOK thinking "Dude, they totally whitewashed Khan!" or "Dude, they changed his entire backstory!" because the writers actively didn't. People went out thinking "Dude, Chekov had never met Khan!" and "Dude, was Carol that blond technician?!"
As said way upthread, no home video, no easy screencaps, no transcript sites, direct comparisons weren't possible the way they are today.
I wonder how long it was between the last rerun of "Space Seed" and the debut of WoK?