I don't think that's a safe bet at all; the choice to put the message to an AI may express a desire, however misguided, to produce a "better" (clearer, less likely to cause offense, whatever) message than the author feels able to manage unaided.
In my experience, the people who actually wanted to improve the presentation of their messages are upfront about it and clearly say they're using AI to organize their thoughts or polish their english.