I suspect that the "turn your hip" as taught by western coaches is truly an "over-turn" situation. Western hips are by and large very inflexible and so the turn of the hip makes up for the relaxation of the kicking leg. If both the standing leg and kicking leg are tense, you get a punt. If you force a turn in the hip, you can at least whip the kicking leg a little bit. Yodkhunpon has criticized my kick so, so many times for turning too much. He laughs at me, his kind of quiet way, smiling to himself. "You do one, and then what? Finish already," he says. It's true. You do that much of a turn on your kick and you've fired your one shot, you're not ready to kick again.
That said, turning your hip isn't "wrong." A strong, cut-you-down kick turns the hip. But it doesn't ONLY turn the hip. It kind of cuts through like a baseball bat, still loose in the hip and the kicking leg is more or less relaxed. If you're Samart, you'll flex the leg on impact, kind of giving it a stick-hitting-a-gong effect. Others don't do that. If you're Silapathai, you're going to kick 8 million times per minute anyway, so the kicks are just fast as.
Different techniques, all kicking. The purpose of the 50 kick drills though is to build stamina and power. They're not truly "this is how you should kick" drills anymore than a 30 second "burnout" of one-two punches on a bag teach proper punching form. A speedbag isn't about technique. It's about coordination. It's about speed. It's about rhythm. That's what 50 kick, or 500 kick repeats are all about. So says me, anyway.