That's the sort of conjecture which lets you arbitrarily dismiss evidence against a theory. Even worse, its the sort of conjecture that is plausibly true yet hard to find conclusive evidence. Any lack of evidence for a subconscious explanation can itself be rationalized away as they just didn't look hard enough to uncover it.
So where's the goalpost for falsifying the theory that they do it unconsciously? Whats the bar of evidence where you change your mind?