Nice! I find myself wanting to say "no, surely that just means that they refuted one particular sort of semiclassical gravity" but I'm not sure what other sort there might be.
Still, for me the main conclusion is: Yup, semiclassical gravity is wrong, just as we already knew it to be. More specifically, surely no one expects semiclassical gravity to be a good enough approximation in situations where the distribution of mass is made appreciably "different in different branches" (I don't mean to presuppose Everett here, it's just the easiest way to say it). So this experiment is finding that semiclassical gravity isn't a good approximation in situations it was never expected to work well in; blaming that specifically on the Everett interpretation seems perverse.
What is something you used to believe, preferably something concrete with direct or implied predictions, that you now know was dead wrong. Was your belief rational given what you knew and could know back then, or was it irrational, and why?
Edit: I feel like some of these are getting a bit glib and political. Please try to explain what false assumptions or biases were underlying your beliefs - be introspective - this is LW after all.