It's strange that Poser includes the Ground by default; you have to de-select it. That's how it works, too, in the Subset dialog boxes elsewhere.

Why on earth would anyone want to export the Ground (a grid of lines at ground level) along with their OBJ? But that's the default.

Sometimes I wonder if someone who actually uses Poser picked some of the defaults in the program. Such as the Rotate tool being the default tool when you launch, instead of the much more commonly used Translate tool, which was the default until P8. Or the way-too-skinny scroll bars that are a challenge even with high-resolution mice.