I wouldn't like to confirm or deny 100% but I have a feeling you may be right regarding the T10. I don't know when it actually stopped in GF (or was supposed to anyway), but I definitely recall it being a regular feature in the old T4 first lounge, therefore presumably T5 GF too.

I fully agree it's sometimes a baffling situation. GF also offers Glenlivet 18 instead of 15 and Woodford Reserve, although I have seen a few knocking around in some of the GC's too.