Re: Grandfathering regarding uncontained engines;
Grandfathering is based on the historical experience and in-situ demonstration of adequate safety. It is obviously measured against the initial design means of meeting the regs (in this case uncontained engine shrapnel) Any significant new experience across the total fleet s of all similar aircraft designs, beyond the B37 Max fleet, may be considered and as such "Special Condition" in the design required by the regulator.
I see no such unexpectedly bad experience among all recent worldwide designs since the latest update to the regulations or mean of compliance. Thus the Grandfathering should continue to be accepted..
Arguing about energy and particle size is simply minutiae in consideration of the current worldwide standards and experiences