I guess it's technically correct according to the naming scheme. An MV-22, modified for the cargo role, would be a CMV-22. But sticking to 'technically correct' when it was a screwy designation scheme to begin with...
The U Utility has usually been used for planes with room for pax and non-palletized cargo.
The only U in recent USN/USMC service in recent years is the UH-1 Huey.
The Navy variant should be the CV-22B, but that was taken.
If the Navy wants to use it as a multimission aircraft, it could be an MV-22B, but that was taken, too.
I suppose they could make it an MV-22C, but the Navy's changes aren't big enough to justify a new version designator. Then again, CMV is such a travesty, why not screw up the system on the other end, instead?
The corners we paint ourselves into eventually when we do things for expediency's sake in the beginning...