We can all agree that this particular dog ( who was trained to bark when he detected the smell of death ) was highly esteemed for his successful deployments ... can we not ?
So, given this dog's historical success, WHY would his handler ( equally successful and esteemed in his own right ) have done anything to jeopardise their hard earned reputations as the best in their field ?
You see, the dog's ( and his handler's ) excellence did not hinge on 'alerting' ... from a professional point of view it did not matter whether he did or not
All that mattered was that the dog was accurate
What would motivate Mr Grime into 'cueing' his excellent and historically accurate dog into making an inaccurate alert ?
... what would he have to gain ?
I must admit I struggle to understand many of these dog issues, but I have often wondered about the very good point you make, namely that the dogs were not being expected to look for one thing or another.
Although the dogs' performance did not hinge on the necessity, as you say, of alerting, we are nonetheless left speculating about whether or not their responses were correct, because we have no Madeleine (alive or dead) or evidence as yet of another person having died on that spot to corroborate or disprove those responses' veracity.
Does this make sense?
I realise that there are other cases where no body has been found and the dogs have been proven to be correct - but we still need corroborating evidence of some kind before we can be sure, don't we?