Try to learn the meaning of analog gravity. It is about the sound waves of classical condensed matter. The speed of sound is, in this analogy, what corresponds to the speed of light. So, this analogy is the completely classical ether - which is a material such that the speed of light is its speed of sound. And, of course, Unruh knows this very well. By the way, he cites Jacobson, who openly uses the e-word. By the way, here is the explicit quote where Unruh assumes a preferred frame, and tells us which it has to be: W.G. Unruh, R. Schutzhold, On the Universality of the Hawking Effect, Phys. Rev. D 71, 024028 (2005), arXiv:gr-qc:0408009 And he also knows that if these conditions fail, there may be no Hawking radiation. This is, by the way, the main problem which prevents me from writing a paper: The claim that if the preferred frame would be the rest frame of the black hole there would be no Hawking radiation would be nothing really new. It would be only yet another illustration of a fact mentioned already in this paper.