The aerodynamic effects of the tanker tend to push the receiver towards the centre of the boom envelope. When your nephew says to use some right roll input to correct from a right-of-centre position, he is basically saying 'don't use left roll input'. Rolling left would initiate a PIO; centralising the yoke can do the same. Better, when right of centreline, to reduce the right roll input a little, stabilize, then reduce a little more.