Once they arrived at Wayne Manor, Batman could finally discuss the matter in detail. He looked at Schiller and said, "You're making such a big show of recruiting Batmen to study at your magic academy, and most of the people you contacted are connected to that Batman. It's hard not to attract Owlman's attention. So what I want to ask is, are you really confident you can teach Batman magic?"
Of course Schiller wasn't. He had never actually intended to recruit Batmen. But after hearing about the internal factional struggles among the Batmen, he felt he could turn the situation to his advantage. This was a good opportunity to expose Owlman's true colors.
Schiller knew the story, so naturally he knew Owlman was no good. Their universe was practically an alliance of villains. But the other Batmen didn't know that. Owlman's universe wasn't a Dungeon either. He had concealed his origin universe well, and no one knew exactly what was going on there.
He had disguised himself well among the Batmen too. He seemed somewhat cold and wasn't Bruce Wayne, but neither of those things was unusual in the Multiverse.
Put it this way: Arkham Batman, with his icy demeanor and ruthless methods, looked far more evil than Owlman did.
Although quite a few evil Batmen had arrived on Battleworld, Justice Batmen still held an absolute advantage for now. Even just to secure his footing, Owlman would keep up his disguise and avoid doing anything too outrageous.
Few Batmen knew that he had followed Laughing Man to Broken Bat's universe. Those who did, such as Main Universe Batman and Arkham Batman, were enemies of his to begin with. No matter what they said he had done, Owlman could dismiss it as slander from rivals.
Naturally, Schiller didn't want the evil