That's why they said this:

> If you make a meandering series of commits during development, squash them for the PR. But please, please do not squash the entire feature upon merge.

I typically turn my PRs into a series of buildable and testable commits. I also put a lot of work into making those commits tell a useful story to the reviewer and to anyone doing git blame later, and squashing them all into one commit undoes that work.