Technically, i would argue yes – but there’s the other side (MB) who will argue that the GCB is just an incentive to keep the car nice, not tied to the value (a good condition MB is worth more than a good condition Vauxhall).
I can see it both ways, to be honest. Of course i wouldn’t mind a higher reward for being careful, but i doubt that’s going to happen anytime soon – and if it does, it won’t be much, due to the fact that the used car market will relax eventually as well. The Mondeo you mentioned is 60k miles under the average and rather mint, i’d assume that plays a role.
edit: on top of high spec (not many cars on the scheme have cooled seats).
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.