Could it be that the missing roof height would have created packaging issues with the Revell box dimensions?
Considering the cost of developing and tooling an all-new kit, I just can't imagine there being any room for unjustified 'error' (goof-ups like getting roof height, roof length, & B-pillar posture wrong). However, I can see some bean-counter pitching a hissy if the body wouldn't fit in the proscribed box (with the rest of the parts) and the proscribed number of boxes in the proscribed shipping carton. Stupider carp has happened.
There are other issues with the kit, all of which can be addressed with the same 'why bother if you don't do it right?' question, and the answers can probably be attributed to the real shot-callers, the bean counters who don't give a rat's patooty about 'accuracy' or other enthusiast concerns.