I don't know if/when that would've happened, but I can't imagine a reason not to allow billet. Once upon a time having castings with factory numbers on them may have meant something, but not anytime recent. If you talk to any of the prominent engine builders in this class, they'll all pretty much tell you these powerplants have long evolved from anything resembling something offered from the factories.
Another great video! Keep 'em coming, AR!
Sean D