Man you "Hemi" guys are touchy arent you. I have BEEN there DONE that with both I am not speculating
That has been fairly consistent with what I've heard since the Pro Stock guys gave up on the Hemi 20+ years ago. The canted valve setup seems to have eventually ended up on top after years of back and forth. Of course the SS AH guys keep pushing the bar higher but I doubt that Pro Stock will ever go back to 426 Hemi engine.
Of course this only applies to the super serious pro classes. Hemi engines still have a ton of appeal to street guys and bracket racers as well as some class cars. Just doesn't seem to be the way to go if someone wants to make max power per cubic inch normally aspirated. I don't know the reason, has something to do with the big chamber I suppose as well as how the heads flow in use. The Hemi heads flow like gang busters on the bench so that isn't the problem. I'm sure there are few engine builders who busted their pick trying to make them run who could explain the problem. I've never tried to run a Hemi in Pro Stock so I'm not the guy to ask.