Images broken down in red
am I misunderstanding what you mean by "start of turn"? Here are some montages:
This one demonstrates what I've been trying to describe in another post - He transitions to the new outside ski in frame 2, but allows it to glide in a straight line while letting the angles build through frames 4-5. He then loads the ski up and arcs through the body of the turn in frames 5-9. This montage actually demonstrates near-perfect rise-line timing as described in Witherell's books for example.
turn has started on frame 2 - well before the rise line
turn starts 3rd frame from the bottom...again well before rise line
This one shows a "stivot", i.e. skidding in a straight line between gates to dump excess speed. If you look at the path of the skier's center of mass he hasn't changed direction by the last frame (i.e. he's still moving in a more or less straight line from frame 3 on), so this sequence doesn't really show his turn timing one way or the other. The fact that his skis are pointed inside the gate in the last frame means that he either has to steer out of the skid (i.e. steer his skis clockwise so that they're pointed along his desired line around the gate) or keep skidding for a while longer. If he tried to hook up and carve from his position in the last frame then he'd miss the gate and be DNF/DSQ. The very best racers would steer out of the skid and arc the turn, while mere mortals would have to hold the skid for the equivalent of about 2 more frames until they clear the gate and would be DFL as a consequence.
a better angle with multiple gates showing all turns start before rise line.
Perfect rise-line timing once again. In the first turn he transitions to the new outside ski in frames 6-7, but then lets it glide in a ~straight line and lets the angles build until he loads it up in frame 9. Frame 9 also happens to be the rise line, so his timing is dead on. In the second turn he transitions to the new outside ski in frame 14, but doesn't load up the ski and arc until somewhere between frames 15 and 16. Frame 15 is the rise line, so he's actually a touch late relative to classical rise-line timing. Delaying the turn is a common adjustment for delays and doglegs, so if the next gate were in the picture we might expect to see something along those lines.
same thing seen in slalom.
And here we have the big exception. In modern SL with breakaway gates you actually start the arc a couple/few feet inside the rise line.
I read up on the rise line concept and it does seem it is kind of the de facto standard to picking a race line. So why do the images of these WC skiers not show this? Am I looking at them wrong? Am I misunderstanding? Please enlighten.