I had a hard time recently swapping a regular G/F bracelet from a 11630T onto a GMT.
In fact, I nearly speared my hand in the process!!! :-)
Above is a shot of the hole in the GMT lug and below the 11630T.
So, the lugs are deeper on the GMT.
Maybe this is the reason for the HLF/HLD end-pieces.
I'm guessing the HLD is more suitable for the GMT style lug.
Or maybe the G/F just isn't appropriate for this type of case...