"break"
It's not at all relevant when you're kicking with a boot.
In fact, the boots are a rather effective purposeful counter-attack to an opponent's shins (or any other part of his leg/anatomy) at any time, and especially when they try to kick.
I consider it "bad technique" to even think of kicking with your shin.... of course, I also recommend that folks not try to actually fight bare-footed.
I don't recall TCMA ( or even JMA/OMA) having a round kick untill after they got exposed to MT and TKD.
I don't recall any round kicks in any of the traditional CMA, JMA, or Okinawan MA forms at all.
AM I mistaken?
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !