No the unload/load times can not account for that much time. It does not take than long to get a few grunts or pallets on/off. Agree that how it has been used is likely the cause. The MV-22 was sold as a game changing design that would speed troops to far ranging fields. Perhaps it is being used more as a regular trash hauler (just like the 46) than envisioned, where speed is not that important.
IIRC correctly the MV-22 uses a different scale than previous rotor craft- largely to show less down time, or maint. hours per hour. Perhaps this "Osprey math" is part of the problem.
All rotor craft spend a good amout of time turning on the deck. The 1% figure seems way low if that was part of the original goal.
The amount of time in rotor mode is interesting. Less dash time than figured.