Oooh,
don't let Bill hear you say that.
The Celladorks always insisted that the similarities between the bands' styles were purely incidental, and cited late-80s PM as their inspiration, not DF. I recall an interview where Bill was
not particularly happy about the DF spectre following him from Cellador to PQ (although, to be fair, every freaking band in the genre besides Nightwish gets DF comparisons these days, just look at a YouTube comment stream.)
WITH that said, DF most definitely were the first ones shilling the "extreme power metal" shtick (appropriate, perhaps, but definitely superfluous genre-splicing), and Chris IS using those exact three words as a descriptor on his ReverbNation page.