According to the quote I read of RMS (I did not read the original email fully) the salient part is his discussion where he claims that "sexual assault" as an expression (at least colloquially) implies the use of force/violence/aggression/intimidation/coercion/etc. by Minsky.

He claims that given the official report as true and taking the the claim of the victim as correct none of those (force/violence/aggression/intimidation/coercion/etc.) were likely.

This is independent on whether Minsky committed a crime or not. This is simply trying to properly understand what the accusations are. I honestly have no idea whether this would constitute rape/statutory rape/assault or any other crime, taking in goodwill what I have read it is likely that whatever happened (other witnesses claim to have seen Minsky decline the advances and the report does not claim any sexual encounter, "just" that Epstein instructed her to) Minsky did not use violence.

I actually believe I misrepresented RMS words here, as he truly only said that the violence implied by the word assault was unlikely.

(Also given that by other reports one of Epstein tactics was to lure guests into having sex with minors to blackmail them)