"In other words, the three dimensions of my own body are the normal three dimensions… The other six dimensions are likely caused by the matter of my own body."
Space-time tells matter how to move, matter tells space-time how to bend. A space-time without matter is indistinguishable from "nothingness."
Since the only matter in this space-time is Zhang Yuan himself, just a tiny bit, it is very probable that his own matter is causing this strange space-time to twist.
"…It is precisely because of the enormous, similarly frequent matter concentrated into a tiny area that the generated relativistic mass causes extreme bending and entwining of the surrounding space."
"This space actually only contains myself; the point of warping should be inside the space, not the outside."
Zhang Yuan didn't know whether his line of reasoning was correct; it always felt a bit weird, requiring more patches to make it logically coherent.