I agree, but I also think it's easy to avoid that. If you say in your cover letter "I appreciate that this might not be in a good state to merge, but I don't personally have any more time to spend on it and won't be able to respond to any code review; I'm posting it to make it public in case it helps somebody else", then the project knows where it stands with the patch, and can invest time, or not accordingly.

(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.)