LeBron knows matchups, spacing, and things of that nature. I've noticed this a couple years ago. What got my attention was him playing against the Lakers. He waits around, some may say he's afraid of the moment, but he's really just waiting for the perfect opportunity to strike. Depending on the lineups he goes for the jugular. He knew flying down the lane for easy hoops just got a bit harder with him coming back in the game. Not that he's afraid of him, but he wanted to make them pay for a favorable matchup.
I say it all the time; LeBron's best strength is his biggest weakness. He almost never forces the action. He waits for perfect timing and he knows the game well so when you give him that half second of opportunity he's gonna pounce on it. That helps him be so efficient and he can get his while his teammates can still get their chances. But some times the game needs him to just force his will on it and he will be hesitant to do so. Pros and cons to every player.
That being sad he shouldn't let them see him react that way. Never let your opponent see that something like a matchup is bothering you, they will ride it.