The transition is the most important part of the ski connection from turn to turn. It involves the biggest body change and movements in skiing. The transition takes you from one side to the other, a complete reversal of body line up. Once you understand this has to happen you can make it successful.
In PMTS skiing, the change happens before you enter the new turn and new falline. This is designed to make sure you are in balance and well organized for every new turn. Traditional ski instruction is different , they tell you to steer your legs and stand up, which forces you to struggle through the whole next turn to survive.
(below) Setting up for the last bit of inside leg flexing(bend or shorten) and tipping (add more angle).
Now the arc is complete, I start to bend the stance leg (Shorten the outside leg) and transfer balance (weight) to the upper ski.
(below) Here you see the balance transfer to the uphill ski.
Hold your countered upper body through transition. If you give it up at this point, you will pivot the skis as they come flat to the snow. Pivoting loses the transition and the High C engagement is lost and the tipping can't continue. This is why a steering approach doesn't work to create high level skiing, it kills the transitions.
Release your stance leg to change edges, let both legs change edges, the new LTE, (new inside ski outside edge) for the new turn leads the way to develop new ski angles , not your upper body.
New inside foot pullback should already be happening, don't panic, by twisting your legs or steering.
Both skis come flat at the same time. The upper body still has not moved, and it's still in the same relationship as it was at the end of the previous turn. If you square up here, you will not be able to get back over your skis without extending.
Hirscher uses exactly the same technique in slalom, as this demonstration.