I think TOPS may be wrong for this one. I've just had a look through my notes and 43093 was paired with 43161 on the 10:03 Paddington-Penzance on Saturday (confirmed by sight, and travelled on). That service does form the 15:52 back so it probably wasn't 063 on the rear?
TRUST limitation - it knows the set number, LA64, and then just returns the current formation for that set.
Looking at the formation sheets, LA64 was as follows on Saturday:
43161/43166/40716/42094/42852/42332/gap/42108/44076/43093