Pull Request Is Now the Unit of Review

> as commit granularity is lost when they are squashed, rebased, or merged committed.

No, commit granularity is only lost when squashing. Both rebasing and merging retains all the commits.

> why not split it into multiple pull requests?

It's arguable better to have a single PR with multiple commits instead of multiple related PRs. I can review commits one by one and also see the end result, test it all together both manually and on CI/CD.