After meeting Main Universe Batman, Schiller realized that the current era of this universe had already reached New 52, meaning the number of universes followed the New 52 setting.
But whether it was New 52 or not, this universe had never appeared among the numbered universes. At first, he had thought this was Earth-1, but later proved otherwise.
Of course, it might have been Earth--1, but then the Ravager appeared. The universe he came from was Earth--1, not Bruce's.
Moreover, from certain beings with higher-dimensional perspectives, including Lucifer and even Bruce after becoming an Angel, Schiller had found no possible designation for this universe. In other words, it was not a universe from the comics at all.
And if Schiller had to identify someone who might have changed the direction and plot of the comic universe, it would naturally be the mysterious original Schiller. He had caused quite a commotion in this universe.
The changes in Schiller's universe and the other universes had all arisen from the butterfly effect of things the original Schiller had done. Then Laughing Man had very likely been affected by that butterfly effect as well, doing something he would never have done in the original work: planting The Laughing Egg inside certain Batmen.
As mentioned above, The Laughing Egg was not a particularly aggressive move. On the contrary, it looked very much like finding himself a spare tire—a literal spare tire, a backup embryo.
The Batman Who Laughs could not have gone to all this trouble creating these things just because they looked nice. And since he had painstakingly hidden them inside so many Batmen, there had to be a reason. Otherwise, would it not have been better to just stuff them into a refrigerator?
So Schiller guessed that The Laughing Egg might not be