We sometimes have trouble getting our crews to spread out the vapor barriers smoothly so that they are free of wrinkles. Might the wrinkles cause planes of weakness that would lead to cracking?
It seems most unlikely. The weight of 4 to 6 inches of concrete would flatten most wrinkles. To cause a plane of weakness that could induce cracking the slab thickness would have to be reduced by 1/5 to 1/4.