Arguably the only reason it could be a lot of work is when the submitter doesn't really understand the code that multiple mixed up and muddled commits have resu

Arguably the only reason it could be a lot of work is when the submitter doesn't really understand the code that multiple mixed up and muddled commits have resulted in. By giving your reviewer a mess, you're only asking for the reviewer to make sense of it instead of doing it yourself. Instead, breaking up the feature into logical pieces allows you to documented every step properly in a separate commit message. If you properly understand what you're submitting for review, then it isn't really much work at all. It's even easier if, during original development, you commit often. But you can always split commits up during rebasing, too.