There are countless genders, and I can think of six sexes without really trying.
Xx, xy, x0, xxx, xxy, xyy. There's more than that but the more x's and y's you have tend less viable and less likely to be carried to term, and thusly rarer. Also, mosaics are a thing., as are things like CAIS. I suppose that the people for whom ambiguity and shades of gray break their brains would classify all of the above as M or F.
They would be assholes being cruel for cruelty's sake and ignoramuses who needed to pay better attention in class and didn't read enough books. I know this stuff and I flunked out of college!