I think of all these responses this articulates my point the most. If humans would struggle with it, why is it still supposed to be "spatial reasoning"? And underspecified or not, you frame this exactly in the way an LLM would tackle this: if I am making a game, I don't place objects in arbitrary positions in a space and try to keep it all in my head, but in relations to one another. Then, the point in front of another is the one where A-B>0.