Unless someone overstayed (+90 days), I doubt if passport control officers would ask/say much to anyone exiting the schengen zone....

It is always the entry which is tricky. I'm not sure if having multiple/previous entry and exit stamps (all in compliance of schengen rules) would give the passport holder more credibility, which means less questioning, or if it gets them more questioning by the passport control officials....

Always very interesting to read about every airport's norms and the experiences of people with passport control.