Catagorical or UNCatagorical - The Grint Denial

[Steve]

A few days ago a made a post about an alleged photo of Rupert smoking pot. Personally, I thought is was some random red head, and that is where the similarity ended. 

Now Rupert's representatives have said -

""This is categorically Not Rupert Grint. It is an impersonator/lookalike." 

I'm sorry, but is that the right way to say it? 

Doesn't "categorically" mean this statement is true within certain qualifiers or within limited context? 

Shouldn't it be '...UNCategorically not Rupert...', meaning this is absolutely and without qualification not Rupert. 

Something that is 'categorically' true is true within certain limitations and definitions.

Something that is 'uncategorically' true is absolutely and without qualification true.

Or, do I have this backwards? 

Not that it matters; just curious.

Steve/bboyminn