Nothing is ever simple is it.
I will study my new Sterns and will check out some 5 and 10 year old Sterns and will see if there is any physical differences with the flipper mechs and pop bumper mechanisms.

Why would Stern have all of a sudden changed their flipper coils ?
Is it to match JJP or the MM remake ?
Was it feedback from Stern customers ?
Anyone hear anything official as to why the change ?

There is no sudden change that I am aware of - they have had flipper problems for 10 years...overheating coils due to the way in which they are controlled electronically - nothing to do with poor coil quality but more to do with poor electronic design IMO.