He turned to complete his backswing so he must return (turn) to impact position. Once the ball leaves the clubface the golf swing is over.
My thought is Kenny Perry turns less once he arrives at impact than many others. I am not concerning myself with the amount he rotates his body after impact, I agree it is irrelevant in regards to the question at hand.
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"In my experience, if you stay with the essentials you WILL build a repeatable swing undoubtedly. If you can master the Imperatives you have a champion" (Vikram).
The reason you can't sustain the lag is because you are so eager to make the club move fast (a reaction to the intent of "hitting it far"). So on a full shot you throw it away too early, which doesn't happen for your short chip. (bts)