I don't know the technical details but how would "different parts of the wavefunction experience different clock rates due to gravitational fields" ever not be the case?
Every particle in the universe is acted upon by every other particle, via gravity, so does this not mean that every particle, in some small capacity, "observes" every other particle?
Every particle in the universe is acted upon by every other particle, via gravity, so does this not mean that every particle, in some small capacity, "observes" every other particle?