But such spheres are not obvious for us. Moreover, we used neither imaginary numbers nor turning inside out. Therfore, we use a model. They sound like the truth. We can guess the substance when we get the special ruler.
Point is what to guess.
But it is not smart you stop to think it only. Do not misjudge the diagram. If it discribe the actual object of the Hyperbolic NonEuclidean World, we have to collect evidence. And if parallel postulate of hyperbolic geometry is not a simple postulate but based on reasonable research, we have to see how it came out. However, we should know what the Hyperbolic NonEuclidean World looks like even on a model, otherwise we miss what to get.