What? He did say what I wrote. I quoted his tweets exactly. He may have said something at some other time, but since you have no quotes just your memory to back it up, I think I'm on more solid ground.
Tweets are dated September 11, 2014 at 11:56 PM. and September 12, 2014 at 12:24 AM. I'm looking at them right now with my own two eyes.
You can go here and look for yourself.
http://thesageadvice.wordpress.com/tag/sneak/
Again, his word isn't final. Jeremy Crawford's is as he's the rules guy.
Personally, I'd have ruled you can sneak attack on another's turn but you can still only do it once between the time your turn begins and your next turn begins. It allows you to Ready an action and delay your sneak attack to your Reaction. "I ready my Action and wait for the first creature to come through the door and stabbity-stab him!" Or use sneak attack with Sentinel or something. But, still, only one.
EDIT: I want you to be correct that you can sneak attack on another's turn. I think it's intentional that the sneak attack says "once per turn" and not "once on your turn" or something. It's tough sometimes parsing whether a rule is natural language or using specific game terminology. Like this thread of when is an attack not an attack?