The straightforward reason still stands: "Does the test still work in a biased scenario, where the test-giver believes in a result before the test is run?"
Also, isn't it a major plot point that replicants are not allowed on Earth?
So Deckard being a replicant operating on Earth is illegal; making his status as a replicant "obvious", by endowing him with superhuman traits (or even self-knowledge) would be ill-advised!
I don't disagree with your points, but one explanation is that Deckard was made for the purpose of passing as human and had to be kept ignorant that he was a replicant as that would likely affect his job performance. If he was made stronger than other people, then it would have tipped him off as to his nature.
That does then raise the question of why Tyrell would present Rachael as being his most "human" creation unless he was testing/playing with Deckard to see what happens when replicants start to replicate.