Guessing... that’s the receiving pocket for when the engine rotates into the full forward flight mode.
It’s a gross amount of parasitic drag, but it goes away incrementally as the engine rotates.
It would be exposed or in such a configuration upon static takeoffs and vertical landings.
The drag is acceptable for the trade-off in capabilities.
That’s what I figured, too. But it sure looks ugly when in VTOL or STOL mode, doesn’t it?