> - if there's a problem with the code, there's no guarantee that the submitter will be available or interested in fixing it once it's got upstream, so it's more important to catch subtle problems up front

It's also more important to have good tools to analyze subtle problems down the line, thus increasing the importance of bisection and good commit messages.

An underrated benefit of "make it easy for reviewers" is that when a bug is found, everybody becomes a potential reviewer. Thus the benefit does not finish when the PR is merged.