[eis]

I don't think they are a hint that spacetime is not fundamental. But I do think spacetime has to be some kind of real physical reality.

The modifications of spacetime that we see as effects of gravity are relative changes to our immediate surroundings or reference frame.

Similarly how you can't tell who is actually stationary and who is moving when two objects are in freefall and all you can note is the relative speed between the two, it would be equally valid to say the objects inside spacetime are getting distorted relative to spacetime.