Very interesting, to say the least. Do you have copy of that claim?
The phrase 'at one point' implies that at certain time in his musical past he had been recognized as having some formidable skills and/or chops.
I don't know Dimebag's musical history, but it would seem this praise by these upper echelon guitarists would've come at an earlier time in his career. Maybe in a 'pre-metal' venue?
Dimebag has always been metal.
And for that matter, so have Malmsteen, Vai, and Satriani by most people's definition.