>The universe is bounded by rules

That's physics. Not all math is physics.

The universe imposes strict limits on the math that can exist within it, and certain broader limits on the math the creatures and well-organized sand within the universe can conceive of in the first place, whether or not it can maybe exist in other universes.

At those levels math and physics are the same bound: the bound of things the universe allows to be conceived of inside it.

It’s possible the math our monkey brains + sand can ever conceive of in this universe is a low and accessible amount.