I have to disagree with this as it relies on the assumption that every commit on a branch is logical and descriptive. In my experience a lot of PRs will have small commits that have poor names as they go through a review process. If you merge this using a regular merge commit or by rebasing the commits on the target branch this creates a lot of noise for those who look at the commit history.

In my opinion it is best to squash all commits into one before rebasing it on top of the target branch. During this process any information that is considered important for the history can be preserved by leaving it in the commit body.