Actually, what the Master said (after that 'companion' line) went like this:
SEVEN: I have no idea what you're talking about.
MASTER: Of course not, because you haven't met him...yet! HAHAHAHA!!
Though I do see how Wormhole got his interpretation of the scene, mine was that the Doctor, when he does finally see the Hooded Villain unmasked, will instantly know who it is and understand why he's being targeted.
And in Eight's confrontation with him, while he's still hooded and disguised, Eight does say "I feel like I should remember you, but..." and correctly surmises HV put his trust in him at some point, and the Doctor let him down. "Doctor! You surprise me! A note of self-awareness at last? Perhaps even culpability?" But he doesn't reveal himself yet - the Doctor's "not suffered nearly enough."