The mechanic seems to work pretty well for all people in TF2 - it's believable at a distance or when you're close but busy fighting something else, facing the wrong way or inobservant. Plus, it'd be impossible to do without clientside mods and sounds hacky to only transmit to certain people.
I didn't specifically mean that touching the spy would reveal their identity instantly - being so close to the spy with my variant makes it possible to determine that they are, as in the game you cannot walk through enemy spies.