I haven't used one, but I'm going to loosely agree with you. I can't see how the claims they make can support the real-world gains that improving a BOV would actually net. It's not like you're adding a BOV where there wasn't one before, they're just making some design improvements (I say that loosely). Based on how BOVs work, I just can't imagine what could be done to further improve anything to such an extent as advertised.

And like anything else, if the racing world (probably WRC in this instance) hasn't latched onto a turbo system component and refined it to within an inch of its life, it probably isn't worth doing. I know that's a lame argument for anything, but most things trickle down from motorsport down into street cars, not the other way around.