On the other hand, reviewing code is also work. One could argue that if you don't intend you follow the contribution guidelines and work with the maintainers to get the code to a state where it's good enough to merge, you are wasting their time.
(I did something like that with a half-done binutils patch once. It wasn't committed, and I didn't expect it to be. But I was happier having put it out there, so somebody looking for weirdo-TI-COFF-format support maybe had a place to start.)
In a similar vein, I recently learned about prefixing a pull request on Github/Gitlab with "[WIP]", or a "work in progress", to suggest that the proposed changes are for informational purposes or not yet complete.
WIP is really used, and we even have documentation about it https://docs.gitlab.com/ee/user/project/merge_requests/work_...