Even if that nonsense actually did mean anything at all legally, why would he think that would be acceptable to the other party? Dude thinks he can do the equivalent of making an agreement while crossing his fingers right in front of their face and they’re going to be like “yeah, this is fine”.
And that’s before the fact that, if the signature doesn’t bind the agreement, then there is no agreement and that goes both ways. You’re not held to the terms of the agreement and neither are they, meaning no house for you.
Or does he somehow think that since they signed for-realsies and he signed with an attached asterisk that says “psych!” that they somehow legally owe him the house and he owes them nothing? Could you imagine if the world actually worked that way? Why would anyone ever enter into a contract like that? These people who think that’s reality do not seem to realize what chaos such a system would actually bring.