Basically, to my ears, it just sounds like a bunch of early reflection reverbs were added (an effect that was mature in the 1980's in its high-end implementations and used in studios to get "bigger" guitar sounds and whatnot.)
Of course, it sounds great for all the viewers who are using cheap (or even not-so-cheap) earbuds, or computer speakers.
What these nincompoops don't get is that these albums were made to be cranked up on a powerful stereo, with full sized speakers, in some kind of room. That guy is basically just ruining great albums who were actually recorded and mastered by people who did know what they were doing. Like, oh, Detonator by RATT and whatnot.
So, there is a case to be made for this kind of processing. But I won't trust a random mastering "guru" with unknown credentials to get that right.