I think all points have been addressed, but for my own clarification I think the situation is this:
If you cannot legally make the flight then you have to have an instructor with you who will log P1 and you will be PUT. So in the 90-day rule, if you fly by yourself then that's fine and you get P1, but if you have an instructor with you he must claim P1 as you can't take passengers and therefore you will be PUT.
If you're flying for a club checkout, when you are actually legal, then you could claim P1 and the instructor get nothing. However as has been mentioned, instructors sometimes don't like this, espacially if they're hour building. I have flown with some who aren't, so they are happy to let you have P1 as they don't need the hours. You must make sure you agree this before the flight to avoid arguments later!
And there is no such thing as P2 in a PA28
