For all that Jakob famously strips women's minds away and leaves them just tits and holes, we've met several of his victims and none has been so reduced.
Anyway... maybe this is more a case of power corrupting. Zenon could be finding that he has more in common with Jakob than he thought, now he has put himself in the same position.
Or, well, he
may be Zenon, but he looks more like Adrian. Why shouldn't he actually
be Jakob? We don't know that Jakob was truly banished from Cherry's mind. Or there could have been a copy of that Jakob in the mind of Cherry's blood monster. Or...
also may be read Erin mind too
Erin may or may not believe that Dani saved her from Cherry's Jakob, but it could be that that Jakob was simply transferred into Erin's mind. (And when I say
simply, I mean, well, the process is fairly straightforward but it would take too long to explain.)
Besides, Erin got a strong dose of Jakob's tits and holes training in Miriam's mind, and he had her under the Watch's influence in Cherry's mind. What's happening here could
all be a reflection of Erin's deepest (implanted) desires.