Every LOS 3.x has a Priam specific driver on it, just like it has one for the profile. Actually there's two files, one is for the running OS, and another is for booting. (There is a third driver for the parallel port itself when used with ProFiles/Widgets.) I don't yet know enough about why a different driver is needed during booting, perhaps it's invoked by the loader blocks (BB,BB).
UniPlus has drivers in the kernel for these as well, and there is source for the kernel (and these drivers). The schematics and drive manuals are up on bitsavers for this drive. These are a totally different protocol than the ProFiles.
I know there were several drives compatible with the ProFile protocol, SunRem made a controller also that accepted an MFM/RLL drive. It's possible Corvus had an interface to this or a model that supported this protocol. Perhaps it needed a driver (or not.)
OSCONFIG is a clue for me, thanks for finding that. I did see differences in BLU widget dumps from profile dumps in SYSTEM.CONFIG - the clue there is the boot device failure and moving from say motherboard parallel port to expansion slot parallel port, or profile to widget, etc. I'll have to figure out more info about OSCONFIG and perhaps how to replace it when moving data from a Widget to a ProFile.