[Abagail]

Players can update unoccupied vehicles by pushing / moving them, and I guess maybe punching them(which would maybe be unlikely).

I can't seem to find what an unoccupied vehicle actually updates being documented anywhere, so I guess I can't really answer for sure.

As for OnUnoccupiedVehicleUpdate specifically here is what is documented on the wiki:

Quote:

Important Note This callback is called very frequently per second per unoccupied vehicle. You should refrain from implementing intensive calculations or intensive file writing/reading operations in this callback.

and

Quote:

Description: This callback is called when a player updates the position of a vehicle they're not driving. This can happen outside of the vehicle or when the player is a passenger of a vehicle that has no driver.