I agree with what you're saying, good code review and good code writing aren't mutually exclusive. However, the truth of the matter is that code review is a far more clearly defined moment in a workflow than writing good code (which is more of a habit than an actual action). As such, it is far more efficient for a team to accept reality and squash after PRs (which is now first possible), instead of relying and keep correcting all your coworkers when they don't properly squash commits before pushing.