You have your fork and the fixes, the PR is just kindness on your part. If they don’t want it then just move on with your fork.
I once submitted a PR to some Salesforce helper SDK and the maintainer went on and on about approaches and refactoring etc. I just told him to take it or leave it, I don’t really care. I have my fork and fix already. They eventually merged it but I mean I didn’t care either way, I was just doing something nice for them.