I personally don't care about Melodyne, but, apparently..
Logic’s ARA support is based on the new ARA 2 specification, but for a plug-in to take advantage of this, it, too, must support ARA 2.
And that is what is part of the new smart flexible audio tempo stuff Logic 10.4 now does, so, that I do care about. Either way, it's a VERY cool new feature, yes?
Tony