Well said- and a good thing to be clear on. Out of curiosity, from your point of view, can a finished horse sometimes need re-training? Ie, for whatever reason, stop being 'finished', and if so, what would it take/proof would be needed for them to regain the status of a finished horse as you define it? Would a horse be finished if it only DOES for certain riders while others it might give trouble (assuming equally skilled/technically competent riders).
I think your standard is higher than what most people think of, but certainly wouldn't argue that is a bad thing.
And assuming equally skilled and competent riders, the (hypothetical) "finished" horse will respond correctly regardless. But that shouldn't (note I say "shouldn't", not "doesn't") exempt those riders (trainers - "every rider is a trainer") from explaining their training methods using some new or existing explanation of animal behaviour, and not just anecdotes, personal experience or correlation.
While I believe it is great to hold a horse to a high standard based off of the training it has received.