TBH I've never really considered what happens when the screws are turned in or out with regards to richening or leaning. I tend to set both a 3 turns out, hook up the gauges and adjust until the intake vacuum is between 250 and 270mm Hg whilst adjusting the balance screw to get the closest measure between the two carbs whilst geting a smooth tickover at 1000rpm. Hence why it's sometimes necessary to adjust pilot screws and balance a number of times.
It may be that after doing a blip test and adjusting the pilot screws I found the opposite of what FP say about it. Memory's really faded over that though and I could be wrong.
If adjusting pilots makes no difference, there must be a reason why this is happening. Blocked pilots, air leak, worn choke plungers, balance way out, etc.