sometimes a lot of torque was needed to achieve the 1.5 threads showing, not all nuts are equal in size, nor are bolts, have a bolt a fraction to short and a nut a fraction to deep and you struggle
So whilst 1.5 threads may be ok with one type of nut and bolt it may not be with another.
I suppose my questions are simple. From the material evidence after the crash has MB confirmed that (1) the approved nut and bolt type was fitted, and (b) the specified number of threads were shown. If the answer to both questions is "Yes", then the wrong criteria is being used to determine correct fitment.
DV