Some have suggested, reasonably, that the unfinished Raptors have been left to sit while the parts needed are used to build others at the same because it might be more efficient for Ford to not interrupt the assembly line.
However, after reading about so many orders not being filled and being rolled over to '22, perhaps Ford is trying to simply produce the most year 21's that they can without regard to their actual ability to complete those vehicles? To do this, they don't care that some going down the assembly line will not be completed and sit for months because the vehicle is already vested as a '21.
Is it just an overall numbers game so they can claim production of much higher number of Raptors for '21? Maybe they are also trying to avoid the hassle of clearing out assigned vin #'s, as would be required to turn each into a '22?