Are you sure? What are your sources please. This is interesting. Because in modern times, Asians have significantly lower bone density of all the races. Women as a whole, have much less then men....but Asian men are close to the average women's bone density. I could be wrong, it's been a while since I've read about this.
I call bullshit...and that cartoon, WTF? LOL. Fighting is fighting. You think ancient White boys and Black boys didn't fight? Like the Gladiators, etc.? Fighting nowadays, is just with a lot of safety rules and dudes have all the better technology with nutrition, conditioning, injury repair/surgery, equipment, etc.
And back to the size thing, I don't buy it that Asians were bigger back then. Especially when after thousands of years, the Asians didn't get bigger until they were colonized by the empirial Whiteboys.... and feeding them their diets. This was quite noticeable after Japan surrendered in WW2 and the Japanese started getting taller.