Hello there,
Thanks for posting Andy.
I am the GML in question and after some closer examination, I believe that the G.I. wears basic officer boots with a flared "cuff" or "ring" around the ankle. You can see that the cuff is definitely a seperate piece from the rest of the boots in these shot (photos incoming) Whether this cuff is made of leather or is a hard armour, I'm not 100% sure on, but my bet would be it would also be leather.
Cheers,
Timmy