The habits one can easily develop to (even successfully) thrash other novices, are often the very habits a well-trained (opponent) has been taught to exploit to maximal effect.
The same is true of many things, such as chess. It is easy to rout weaker opponents after they've made obvious mistakes. But even if you remain undefeated, you will have learned nothing about tactics and strategy.
I thought the same thing about it being impossible to get inside a swordsman's sphere. That is until I saw a video of a man swinging nunchucks as fast as he could in front of his master. Then all of a sudden the master just reached out and grabbed the guy's hand mid-flail and then took him down. Made it look much easier than it is.