From the abstract:
"Assuming [assumptions] we show that ... can in principle solve..."
Yeah, well, you know... that doesn't sound as promising as the title.
That's the whole point of the article:
"We show [Assuming {competing physics theory} then {P = NP}]"
(or something along the lines)
"But we actually think P != NP... so [Assuming {P != NP} then {competing physics theory} cant be true]"
Shocking..
Assuming X is true, that implies Y. We don't think Y is true therefore we now doubt that X is true, is a very standard thing to do in math.