the information regarding UHDs and CloneBD is somewhat cryptic and misleading for all AMD graphics cards owners. Please bring it to the point. I understand from your post that GPU support for UHDs doesn't work with AMD cards for now. Only with BDs. Right?
If you convert a UHD to BD, then, sure, you will benefit from AMD hw acceleration for AVC encoding.
If you convert an AVC track from a UHD, again, AMD hw acceleration will help.
It just currently (as before) doesn't support HEVC10, yet. That's not new.
Other than that, though: I'm not with Elaborate Bytes, I don't know all and everything about this.
What I do know, is that nVidia is the only GPU with a decent Video API.
AMD and Intel have a terrible interface, which is not entirely their fault, except for that they decided to pop their API onto DirectX (which is originally a gaming API for crying out loud, it was simply not designed for this purpose).
That's mainly the reason why things are taking longer with those GPUs. You spend weeks and weeks ironing out spurious bugs, that are near impossible to track down because of the convoluted nature of DirectX (sorry, I'm on a rant-roll).