Saturated snow does separate the boys from the men. Yes you want to stay balanced. No, you do not want to lean into a turn. Yes, you do want to use as much flexion/extension as possible. No, you do not want to push your outside leg out straight. Yes, you do want to maintain more flexion at the end of the turn on your outside leg to keep your mass centered over the downhill ski.
What I was referring to is not completely straightening your leg, but pushing it straight down into the snow in relation to your slightly angled body. You may be able to ski muck with absolutely no body lean on your S7s, but on the OPs 78 mm waisted skis he will need to reverse the camber of the ski, which will require a little force in the heavier snow. It is not an edging deal, it is a ski flexing maneuver. Change the angle of the ski in relation to the snow and then push straight down on it to achieve the desired arc turn.