it is beneficial to preserve nicely organized logical commits in pull requests
Although it makes sense for pull requests to be squashed when they are made of multiple incremental commits added each time a reviewer asked for a change, it should not be a requirement.
In the past it was difficult for the reviewer to visualize the changes after the author of the pull request force pushed a commit series with just a typo change. But it can now conveniently be seen when clicking on the *force-pushed* link added in the pull request comments. It only displays the diff between the old commit and the new one that was force pushed.