I agree with everything you say there except the word 'checkout. Any flying with an experienced pilot and robust debrief is a valuable tool for improvement. That experienced pilot may be an instructor, but equally could be another syndicate member who happens to be a professional pilot, or any other profile of safe and experienced pilot prepared to enjoy the flight, observe and give some constructive feedback.
Agreed, though you might hope that FI's are better at spotting bad habits, and less inhibited about telling you.