Yeah, it should have a disclaimer at the bottom: "If everything and nothing on this chart applies -> Prog"
The only thing I slightly disagree with is Nu Metal (though appreciate the comedic value) as I consider that a misnomer, not metal at all, but hard rock. I'd like to see Metalcore take its place on the chart.
Also, I agree with Compurocker on both of his points.
If I can be a party pooper and make a serious point about a joke, the Doom metal box is in the wrong place. I think they added it in last as an afterthought.