Mike,
I understand your questions. But bear in mind that many such kicks are done in combination, like a Wallace, reversing trajectory mid stream.
As you know hook kicks come in three variation:
1. Straight on, like you might remember in Billy Jack
"I can take this leg and put it on that side of your head and there ain't nothing you can do about it!" Billy Jack
The one I would prefer most in free style competition as you can hook around a straight punch or jab and the opponent won't even see it coming as in Billy jack.
2. Spin hook heel kick wher you spin on a dime and throw it.
3. Jumping/spinning heel hook kick.
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In any case, Bruce's kick in the photo is way off target, r/house or hook.
I doubt he'd have picked this photo to show how good of a fighter he was. Problem he was having with Jim was he could not get anywhere near as he had hoped.
Not a diss on Bruce but a compliment on Jimmy.