Rock Lee, who has no Nin or Gen skills, could do a Bunshin and Naruto, who people didn't classify as having no Nin or Gen skills couldn't? I think the most plausable theory is that he got lucky and came up against a taijitsu test. Afterall, that is the third way a Ninja can fight so no reason why it can't be tested as well. Thouhg now I'm wondering what kinda of taijitsu they were taught at the academy.