The people who taught/teach hip turn restriction should be flogged in the public square.
There is really no such thing as too much hip rotation, just incorrect hip rotation. Some people don’t have the flexibility to have much separation and this makes things worse…all arm swing city when try to get “X-factor.”
That is the problem with golf instruction, it’s all about teaching the opposite of bad. Hold the lag, low and slow, swing to right field and restrict hip turn are not good things. They are just the opposite of casting, lifting and not turning, over the top and over rotating to the inside.
You don’t fix over rotation by restricting hip turn. Over rotation is a result of poor setup, turning too flat, tilting toward the target, or some combination of those three things. You fix those things, you don’t tell the person to restrict.
You don’t fix loss of lag by holding it, going wide to narrow or ringing the bell, you fix it by ridding yourself of arm over run and upper body movement toward the target.
…and the list goes on.