I always assumed it somehow contributed to the elasticity of the heel but the s/px lines have the exact same vertical elastic travel of 28mm even though the heel is fixed. And if you think about it the lateral rotation shouldnt really affect the vertical elasticity anyway.
The only difference I can understand is that the turntable doesn't impede the boot from rotating when the toe releases laterally. But how much friction do other heelpieces really impart on the boot when the toe releases. I've had the toe release during a fall on attacks, wardens and other bindings and it never really felt like the fixed heelpiece prevented my foot from rotating out of the binding. Is that the only benefit of the turntable? (Aside from the short mounting pattern which seems more like a function of the way the whole heelpiece is designed and not just the turntable)