[KolenCh]

As the black hole getting larger, it is more difficult to notice this difference (of crossing the event horizon or “observe the geometry around you”.) and as we are talking about the whole visible universe being inside a black hole, we are in this extreme large scale.

Also, I’m not sure why you’re arguing about the radial coordinate being time-like. You can only measure in your own local reference frame. You wouldn’t necessarily be able to transform between your own local reference frame to the blackhole’s if you don’t know you’re in one.

The universe as a black hole is actually a very old idea: https://en.wikipedia.org/wiki/Black_hole_cosmology

I’m not saying we are in one, but I’m saying it is not as obviously false as you might be arguing.