I agree with your hypothesis. After all, they trained from childhood in this armor and reputedly some were trained to leap to the saddle in full armor (probably not the armor we see in jousts in the movies).
Another comment along this line. Look at some of the surviving weapons such as battle axes, maces and broadswords. They were huge and made out of steel and had to be a bitch to swing all day in battle, but they did—while wearing mail and carrying shields.
Tough knights don’t dance.
Even by 1066, the swords were long and heavy in order to penetrate the armor of that time — also the impact could break limbs, rupture blood vessels, or knock an opponent cold, irrespective of the amount of armor.