OR, here's another hypothesis, IF Satoshi is really a group of people, THEN it would make actual sense to make everyone believe that he/she is one person and hide the fact that they are a group. And by hiding that fact, if one of the Satoshis was exposed, then the other Satoshis could merely sign a message from a key known to be associated with Satoshi or an old forum account to say That person is not Satoshi".
If it was a group of people, then there was probably two or perhaps three of them?
The hypothesis is interesting, I think it is possible, but I disagree with an action that if they are a group of people, they will need to sign a Bitcoin message to prove that anyone on media is not Satoshi Nakamoto.
If they decided to disappear, simply maintain it with time, forever, it's enough. They can let people free with speculation on who is or are Satoshi Nakamoto. Like now, with silence from Satoshi Nakamoto, there is a hypothesis that Bitcoin founder already passed away. It is an interesting hypothesis and it will be broken if Satoshi Nakamoto will be active again with a Bitcoin message or PGP message, that is unnecessary to protect Bitcoin founder anonymity.