Obviously, he allegedly has this material. I tried to put that in the title, but I hit the character limit.
In this case, allegedly would be if this was hearsay, or rumor, or according to a source, but no, he is flatly stating it as a fact about himself, and is generally considered honest. If we want a qualifier, you can attribute the fact to him (GG says he has) but allegedly is too weak.
http://www.noozhawk.com/article/121512_harris_sherline_most_...;
Did you even read that list? Those include actual proper uses of "allegation". If you actually look at the definition of "allegation", it is a claim of fact, which is the most you can say about charges that may be brought against a defendant pre-trial. Or are you not at all aware of judicial proceedings in which facts are shown later to be incorrect?
That English words have concrete meanings doesn't prevent misuse. On the contrary, specialty words with specialized meanings are misused most often by laymen. The misuse is just more recognizable when you're familiar with the area.