My 5, more technical, cents:
I would just simply call it “Super Nintendo Entertainment System MSU-1” as MSU-1 is the official name of this custom virtual enhancement chip. It certainly was inspired by the Nintendo PlayStation because it does what a real CD-ROM add-on would have done (and even more) but as far as I know it has nothing to do with any real CD-based prototypes from a technical standpoint and was made completely custom by byuu (the developer of the bsnes/higan emulator). The only known Nintendo PlayStation prototype hasn’t even surfaced at the time of the development so there even weren’t any “official” technical specifications he could have used for designing it.
It works like an enhancement chip on a cartridge (like the SuperFX chip used for games like Star Fox) and not like a “real” SNES base-unit hardware upgrade or attachment. This decision was made to be able to support the chip even on real SNES hardware through flash cards or other custom created cartridges and therefore it wasn’t designed to support the CD format as a whole in general (again, it’s an enhancement chip for a cartridge and not a disc drive) as it also goes way beyond that like having support for files up to 4GB.
Of course everybody will understand what this system is supposed to be if you just call it SNES CD but from a technical standpoint it’s just wrong. So basically it's simplicity versus accuracy
EDIT: Actually there is a homebrew game specially designed for the real Nintendo PlayStation hardware called “Super Boss Gaiden”. I doubt that we will see a lot homebrew games/hacks which will go this route as well but personally I think that the system "Super NES CD-ROM System" should be reserved for these kind of games and not MSU-1 hacks.