GFCH,
You may assure the fella who wants to avoid MAX by 4000 feet that there IS protection there, to varying degrees as discussed.
You may also assure him that if given the choice of flying with him or the turkeys who want to fly at MAX, I'll fly with
HIM any day.
A tad conservative, but conservative people usually live longer....
(BTW, 4000 ft below is approximately right for SEVERE Turbulence), he does have a point............. I'll bet he flew in the old pre-FMC days when that was the rule.........
Regards,
Old Smokey