You don't understand. Why else would the thief sell easy-to-launder BTC? Evidently, they are of little value to him. We know that Zhou Tong considers BTC valuable, and wouldn't be stupid enough to sell the ones he stole. Therefore, Zhou did not steal them.
This is a classic framing. There is no reason to suspect otherwise.
Um as far I as know Zhou declared that he leaves the bitcoin world... Which makes the above statement irrelevant.
Here his announcement, when he declares "I'll try to keep my gold bitcoin". You see no where he says he will keep bitcoins, more like I will only keep the gold one.
https://bitcointalk.org/index.php?topic=81581.0. This implies he still considers them valuable. So, why would he sell them? He's not stupid enough to blow his cover that way if he was the thief.