I think it’s unlikely that CC90 would glitch, but all other CCs would be fine. I would presume that the CC number (and its associated value) are just data for a general “send the MIDI” function. Of course, I haven’t seen the code, so who knows.
There are certainly libraries that use CC90. Whether anyone’s using them in Dorico, I don’t know.
Anyway, all’s well that ends well.
So I went into my Rosetta setup for Dorico to be able to directly access Hauptwerk’s VST[2]/AU Link. CC90 = 0 did not cross over to Hauptwerk as it does without Rosetta and using VEP8. I suspect it is a HW issue and not Dorico. I cannot imagine that a CC90 change in Dorico would be different under Rosetta vs. not. Anyway, that’s all I have to offer at this point.
Again, much, much gratitude to you folks @Brian_Roland and @benwiggy for your very kind and generous testing on your end and recommendations. I will forward this info to the HW developer just as an FYI should they receive other inquiries or need another reason to update their VST/AU link. Peace and blessings!