All the many professionals I know and work with day in and day out (and Joanne is a professional) do this all the time as a matter of course.
It is how you get better mixes and better songs.
I don't know a single soul who has "gone places" who doesn't do it. Good-hearted constructive criticism, sharing, and listening to one another in a professional environment is the way it is done.
Maybe "shyness" is not the only factor. Maybe for some people it is a fear of wondering how they might be treated.
Consistently professional environments feel safer to most artists.