Generally your body can only adjust 1 hour per day (varies by direction of travel). So shifting at the start of your travel is a bit late. You probably want to shift gradually a few days before travel if it’s a major shift.
Not really - if anything it argues against. You have no control or information about who did and didn’t start shifting when and people may be connecting from another flight and have different jet lag differentials to begin with. Serving it on the destination time is probably the best, but if someone hasn’t started shifting, they’ll be a hungry and cranky passenger vs you being cranky and tired after you’ve left the plane and you’re not the airline’s problem.