That's the source geometry/textures, not what is output. Nanite takes massive billion+ poly models that have 8k textures applied to them, then scales them to as close to pixel-sized tri's as possible (which naturally scales the textures.)
There's only ~3.7 million pixels @ 1440p (the internal rendering target of the demo).. it would be pointless to have billions of triangles. Nor would it be remotely feasible to render or store.
For the PS5 demo they imported the massive models into UE5; the engine then scaled them to 4k scale (so closer to ~8 million triangles) so that they'd even be feasible to store on the PS5. Then in real time that all gets scaled to the size the model takes up in the 1440p render. So if it's close to the player, more tris, if it's farther from the player, less tris. And the texturing gets scaled along with that.