Folks - bought the aforementioned in blue this time (sold the black dial last year) and it's pretty much the perfect GADA (with GMT!) for me. Sapphire bezel insert, awesome blue sunray dial, chronometer, the whole thing.

Bought grey market and confirmed beforehand that they indeed hold onto the warranty card so as to stay out of trouble for selling below MSRP and if an issue arises, they send it to Longines themselves. No in-house warranty or sending to some 3rd party.

Well lo and behold...

Screw-down thread INOP on New Longines Spirit Zulu Time 39mm