Yep… It’s more or less the same thing I’m experiencing with the few third party VST3.x plug-ins that I own : they all have a proprietary presets management, from which, none of the presets are appearing natively as regular VST presets in MediaBay. I’ll take an example with LoungeLizard v 4.0 (VST 3.6.7) : even after a MediaBay scan, none of the bundled presets appear in mediaBay and available in the Program list of the inspector.
OTOH, and even if the Convert program list to VST presets command isn’t available (it’s actually only available when a VST 2.4 plug-in is involved, I think), we are still allowed to select each proprietary preset and do a VST preset from it with the Save preset… command in the plug-in window. Doing this, we can recall the VST presets created which “encapsulate” the proprietary program chosen at the moment it has been created, and this time, they appear both in MediaBay and in the inspector Program list.
It’s a mess, I admit, and have complained about it since Cubase 4 days. AFAIK, there’s nothing more effcient, though. 