ssh - you clearly have a mental block. The PSIA man replicates a human being from the knees down. To hold both lower legs together there is a horisontal bar connecting the knees together allowing for movemen only in the coronal plane (sideways). Its correct that the PSIA man doesent rotate anything but if you look at your legs from your knees down as you ski or do skiing movements they also dont rotate in any way. Maybe you are confused because the PSIA man doesent lean forwards in his boots.
Femure rotation refers to your femures rotating in your hip sockets. If you lie on your back on the floor with your legs straight and point your feet to eather side that is rotation. That is correct. But now flex your knee joint, bend your knees, and do the same movement with your legs. See, this is important. When you ski your legs are not extended fully. Because if they are you cannot tip your skis with quick leg movements.
Its good that you have come to the conclusion that you dont need any other movements to carve than tipping. Check out the PSIA conspet TGIF for a killer ski tip on how to carve. However, bringing the PSIA man into this thread is kind of wrong. Its interesting that when the thread is about carving everyone is very conserned about skidding and when the thread is about skidding then everyone is conserned about carving. They are in reference to this discussion total opposite. As you said your selfe, carving requires only tipping. But when you skidd you need a blend of skills. Once your blend of skills are ingrained including all the bad stuff then carving will become very difficlut. And vice versa.
Hmmm... A mental block, eh?
What happens to you when you flex your knees and rotate your femurs? For me, I turn my feet to the side. My knees stay in the same lateral plane, but my kneecaps point to the right or left. Since my kneecaps change orientation, they could not do that if they were bolted together, so even if PSIman is as you say, he's still not rotating anything. That said, I'm with JASP in believing that the bar across the top of PSIman is actually the equivalent of his pelvis.
Regardless, rotation (at least around these here parts) is defined as the rotary movement of one body part relative to another. Until you can describe how you see PSIman rotating one "body part" relative to another "body part," you're going to have a difficult time convincing most of us that any rotation is going on.
What he's "doing" is the equivalent of locking your femurs relative to your pelvis and tipping your skis through simply shifting your pelvis from side to side just like that bar that connects his "legs." He doesn't tip his feet or rotate anything. He just shifts his pelvis to allow his CoM to pass over his skis, tipping them because the legs remain in the same orientation the entire time.
Again, the only thing that matters here is that you and I can arc without using any muscle movement at all. This is a gigantic concept! We can stand statically and allow gravity to pull our pelvis to one side and then the other and make arcs just like PSIman! Holy smokes! Awesome! Now, dial in the minimum additional movement and energy to accomplish whatever additional outcome you are seeking, always remembering that you don't need any at all to arc...
Please understand that I've been carving for a long time, tdk6. Even on old pencil skis. I understand many of the mechanisms and options, but the most important one for skiers to understand today is what they don't need to do to accomplish it.