“May I also suggest that those who treat it as a ha’rama, or as less than a 100% ”
No. People who have a minhag not to sell chometz gamor are not hashkafically opposed to machiras chometz. Even they don’t consider other peoples’ sold chometz gomur to be chometz sh’over alav pesach.
“There absolutely is a buying back. I’ve seen it myself.”
It seems like the process you’re describing is the same is what we’re saying. My only point is that I’m not a fan of the lashon “buying back.” The goy didn’t pay yet. It’s just semantics, but I think it leads to a lot of the mistakes people have made on this thread.