Yeah, I'm with you. I mean, git isn't magic. You "can" squash anything, including a merge commit, by just being at the end result, running git reset <commit you want to be squashed off of> and then running a manual git add and commit there. That's basically all a squash is.

But what you'll be left with us a single commit that contains all of the code from the branch you're squashing and also all the code pulled in from every branch you merged, all written as though it all came from this one commit. And maybe that's what you want? But it feels like also maybe it's not?