I have several friends who instruct, and mostly the notes are for the benefit of other instructors, e.g. where you are at in your flying journey in case another has to take over your training for whatever reason. The stuff that is relevant to your development should be passed on verbally to you by your instructor during the lesson debrief.
At the end of the day, I would not be too paranoid about what they might write down. It comes down to that bond of trust that is required between you and your instructor. After all, you have your lives in each others hands every time you go up.