Superheavy is a weight reference, not a height reference. Since the mid 90's there has been talk of making a weight division for people above 220. I've never put a lot of though into it; but at the time it was really being talked about, it could have really been interesting. Michael Moorer, Evander Holyfield, Mike Tyson, and even a young Cris Byrd was mentioned in an article I read on the subject around 10 or so years ago.
Toney does absolutely nothing to prove Greb could do similar vs modern heavyweights (if that's what you imply) i.e. the guys Toney fought. Toney has grown into a huge powerful tub of lard who fights totally different from Greb.
Greb is no James Toney. I will most likely argue that Greb is impossible to do head to head accurately, because there is no film to analyze his style. Greb is always in my top few p4p based on his resume. Reports of Greb tell that he was fast. They also suggest some boxing ability. I've yet to read any reports that speak of his defensive mastery. Most reports I've read highlight his offense. James Toney is extremely hard to hit, and takes a good punch once he is. His relaxation allows him to fight 12 rounds even in poor condition. James Toney is also very accurate, and fairly active when he's in near half-way decent shape. This paragraph that I am typing is most definitely different from any report I've read on Greb.
I think it does prove you can be successful with skill. byrd was a bulked up sub light heavyweight fighter, and toney should have been 20 lbs lighter for most of his heavyweight fights, and if he had been and had better stamina because of it, allowing him to maintain a better workrate he'd have done even more. a smaller heavyweight with good defense and in tremendous condition to keep busy could do great things in the division, and who knows if they have power and are aggresive they could beat even the mighty klitschko.
Toney did not beat any of the current or former belt holders. He was carefully matched vs no-power, smallish heavyweight who also happened to be past their best in most cases. If you add the failed drug tests, and him losing twice to Sam Peter whose stock took a hit recently, I don't think Toney proved he belonged as a top 10 heavyweight.