It's a family tree of metal and hard rock. Some will disagree, of course, but it's fun to trace the roots and connections of this stuff.
I do really disagree... it ignores a whole lot of influences and groups bands together, which never had been in the same style. At the same time, it is really US-Metal centric. Symphonic Metal of the past years has been ignored. Pop Metal sounds like a category for all those bands that had not been cool enough. Hair Metal is not even existing in the tree, despite it being an important anti-pole of metal (It is anti-metal). And what drugs made the person group Doro as Pop Metal! What she does was always Power Metal, even when her band was the famous Warlock. And why is Judas Priest power metal, if they are actually considered THE band of NWOBHM, and why is Iron Maiden NWOBHM, if they are more in progressive metal?
Also it doesn't include punk (Only "early punk" and then it is wrong from the time, at that time you had proto-punk), despite punk and Metal being closely related. And progressive is just thrown into the room like being one and the same for all decades.
Who ever did this, he had never been to Wacken in his life.
Also, Pop Metal is a strange category... Blind Guardians latest album managed to reach #2 in the German album charts, which would sure say it is pretty popular...even more than some bands in the pop metal class.