"Why doesn't Amazon stop this from happening?" is a different question from "How does this happen?".

Any system Amazon puts in place will have a lot of false positives that require human review. And that is entirely aside from the fact that underhanded sellers will try to flood such a system with automated disputes until Amazon relents.

> The ones I've seen are WAY off when you look deeper.

You're assuming these disparate merges happen in a single step.