Originally Posted by
ST Dog
My understanding was the same bundles were used on the MAX as the NG. No changes. Since they didn't change the wiring there was no reason to treat it as a new part of the deign. The point of grandfathering is that unchanged items stay unchanged. So as far a Boeing was concerned it didn't need to be evaluated under new rules. There are 100s (1000s?) of places on the NG and the MAX that wouldn't have meet the changed rules at the time of certification but were allowed because is wasn't a new part of the design.
No the FAA is retroactively deciding that the old grandfathering rules don't apply to a certain case (the wire separation) and make that unchanged item meet the new standards.
The location of the engines has changed. There is more chance of damage in the case of an uncontained failure.