[aejm]

Think about it this way: you essentially have two different “problems” you’re trying to solve simultaneously, flying the tanker and flying the plane being refueled. As other comments have pointed out, the plane being refueled has much higher control authority and responsiveness, compared to the generally larger tanker. Also, given the two aircraft are flying in near identical environmental conditions because of their close proximity. The “easier” of the two aircraft to fly is the plane, not the tanker. So your control algorithm (or pilot) flies the tanker and the plane just matches its control inputs plus a position offset.