An "Abandoned" tag certainly wouldn't cause the mass exodus of Patreon support like many people are convinced, but it wouldn't be good for business either.
If someone thinks it would do anything to his current patrons, then they are as delusional as the ones who believe that he has been working on this game for the last year. But, the abandoned tag would prevent the newbies coming here from falling to his trap. Like we have seen here, there are people who don't bother to read anything else from this thread than the first page, then look at review rating and download the game. After they see it and like it, they'll subscribe to his Patreon because "$1 or even $10 in a month ain't nothing for this masterpiece! And would you look at that, the dev says that 1.0 version is coming this year? Neat!". With the abandoned tag the newbies would know to stay away from him.
And that same applies to his upcoming projects. We who are aware of the situation know better to avoid ANYTHING he ever makes anymore. But there are still newbies and even some old Serranos here, who might not know or remember what the situation with him is, would go to upcoming "Milfy Kingdom" thread and see the devs name, then go search it from this forum to see his previous work. If he has all his games as "Completed", there might come the illusion for people that "wow, such great content and so many completed games, what a good dev here, I'll even support this!" and they would fall to his trap once again. If they see even one game, not to mention it would be his previous game, from the dev with abandoned tag it would immediately prevent them from supporting him at any level, because it would expose him as untrustworthy dev.