The most difficult problem while moving the tests is deciding if they still conform to the current spec.
Some tests use (or test) rather obscure features of which I don't know if they are specced, and if yes, where. The specs are a massive lump of text (more than 31k lines) and rather dense, so that's not always easy to decide. Try to search for the operator but in English text isn't entirely easy, for example.
OTOH fudging isn't really necessary for moving tests into spec/: all implementations that we care about don't expect all test files to pass, only a selection of them. (Pugs does, but since pugs isn't maintained anyway, I don't care for now).