This sounds like the opposite of what Q-reeus just said. He said the rotating and gravitational cases produce different measurements. I don't know which is correct, but it seems like Einstein had the opportunity to say the measurements would be the same in both cases, but I don't recall him doing so specifically. Yes, that is what I think as well. SR is built up from its own postulates, in flat spacetime, and should therefore stand on its own in flat spacetime. GR is built up from SR, for the cases where there is not flat spacetime. GR should therefore reduce to SR in the case of flat spacetime.