I'd certainly rather jump into a codebase with a great test suite and crappy commit messages than a crappy test suite and great commit messages. But these are apples and oranges. Keeping a great test suite is a constant fight against tech debt, and testing things properly can be harder than the actual implementation.

In contrast leveling up from the terrible "WIP WIP do the thing" to something slightly less awful takes maybe an extra 1-2 minutes per commit. And every time you do it you're doing your future self and future co-workers a huge favor.