You could say that about any rider on the sram program being told to run what the company says to, does that mean if they asked Peaty to run a dart on his V10 he'd do it?
And if you're going to split hairs on freeride/slopestyle, I've seen his Scratch and he has the XO cranks on that as well, so lets just stop this here.
Look at any pro's freeride bike and I can guarantee that you won't find carbon cranks or bars. Carbon just isn't strong enough for big drops and jumps. Riders are already destroying their aluminum parts. Not to mention how much more expensive carbon is than aluminum. The Race Face SixC cranks on this bike are $670 USD while a pair of Atlas FR cranks is $290.
Brandon Semenuk is running carbon XO cranks on his remedy slope bike, and he beats the hell out of that thing. Even if they're the rumored XO dh carbon crank, it says something when he's running them on that style of bike, he could easily run descendants but he's not.
Slopestyle =/= freeride. Also Semenuk is sponsored as all get out. He breaks something, he gets a new one for free. He also runs what SRAM tells him to. They could tell him to run XX cranks and he would.
And if you're going to split hairs on freeride/slopestyle, I've seen his Scratch and he has the XO cranks on that as well, so lets just stop this here.