Wait why would scum hide it more than town? So we lynch faust instead? Hmm I like it. Of course then faust could just name a poor sap that wasn't vanilla'd and is scumreading his partner or something. But that backfires super hard.
If the Vanillia-ized player was scum, they wouldn't to volunteer any information to the town. Think back to before faust claimed, we didn't even know if there were Aliens in this game. Hiding that type of information from the public sows confusion, makes decision making worse.
And then even if they did say that they were vanilla-ized, that elicits a roleclaim from that. As I've said before, if you're vanilla-ized and town then you're no longer a power role, why not claim?
Also keep in mind that this line of thought is a no brainer. From a vanilla-ized scum's perspective there's no way an Alien would claim today and confirm that someone was vanilla-ized last night. Might as well keep the information to yourself.