Read somewhere here (TYF) that setting incomplete chassis in bcm turns off hyperflash.
Seems to work as a lot of GM van-based (3500, 4500) Class C Motorhomes have the stupid silly LED brake/tail light assembly in rear, incandescent on front, and whatever was handy on the sides.
What is even more interesting is that same chassis & year, same Cab options, etc... when doors are 'double' locked with remote one make/model will flash front signals, side marker, tail lights, clearance lights, etc. Oh, and honk horn too. But near identical floorplan on identical chassis will flash front signals, rear tail, but no other lights at all. I have not been able to find any similarities to identify disparity yet. I suspect one floorplan uses upfitter, other one doesn't.