We use a blend of skills to determine and control when and where to turn as well as its shape, size and duration.. Even the theoretically clean carved turn is shaped by the bend put in the ski as well as the turn radius inherent in the sidecut of the ski. The intention to make such a turn is executed by the skier through a controlled application of skills not by his equipment. Do I spend all day making 12.7 meter turns? of course not nor do I aspire to. We aspire to a higher degree of versatility and control and hence freedom of movement. Even this theoretically clean turn requires an accurate blend of edging, pressure, balancing movements, and rotary skills to utilize the equipment in this way. The path to such ability is surely by developing all the required skills throughout the skier's learning process since all must work together and in increasingly sophisticated blending as the skier progresses..
Its not entirely true. The execution of the turn is offcourse made by the skier but if you carve the only thing you need to do to turn is to tip the ski on its edge when you move forwards. Look at the PSIA man. Only tipping. Executing a skidded turn is much more complicated and I dont think its done as easily with a robot. It requires a blend of movements and a good feel for the snow.
If its fun or not to be carving 12,7m turns all day is annother story. I personally think a 12,7m ski is a very nice compromise since it covers a good range of functional turn radius turns. Depending on how good you are the ski performs well on all kind of pitches except for the very steep ones. But a longer radius ski would be even worse. So for skiing on the pist I vote for a SL ski if you are a good skier in good shape and you can and you want to carve as much as possible.