> So the idea is really "what's the point of having a history full of broken state?".

I rebase commits so they don't break the build but the history remains clean and incremental. Selective fixups and so on isn't the same as squashing everything into a single commit.

> This would be a hint that your PR was too big and addressing more than one thing.

I don't think so. Sure, that can be true, but squashes can also simply lose vital history. Suppose you remove a file and then replace it with code copied and modified from another file. If you then squash that, all Git will say is you made a massive edit to the file.