Game Freak was making cool Non-Binary characters before anyone noticed that stuff in video games. Mysteryman Eusine as a trainer class doesn't have a gender signifier like every other class in the game, making Eusine non-binary as they're neither male nor female in the Gen 2 code.

In the gen2 code every other class has an assigned code whether they have a male or female gender, Eusine is the lone exception. MysteryMan could be their title, like from the movie. I'm speaking on game code and even Fishers have an assignment and same with Rocket grunts who use the male sprite model, they're coded with an assigned gender code. Eusine is the only one that lacks one. Every other trainer in the data has one. That's their trainer class name, and I'm just speaking factually.