That's correct--no one knows. But so long as the difference is only seen after death, and otherwise has no histological, toxicological, behavioral effects in living tissue/animals--even the FDA is going to have a hard time justifying preventing another clinical trial. Though I have cited a personal belief that there is a 30% chance that they could do so in spite of the illogic.
Caveat: the electron microscopy study is the last step to establishing the lack of even submicroscopic effects in living--then 'flash-frozen--tissue.