Are you very familiar with Apocalypse World? This post makes it seem like you're not, given that it is wrong. As per the rules, p 109:
Apocalypse World divvies the conversation up in a strict and pretty traditional way. The players’ job is to say what their characters say and undertake to do, first and exclusively; to say what their characters think, feel and remember, also exclusively; and to answer your questions about their characters’ lives and surroundings. Your job as MC is to say everything else: everything about the world, and what everyone in the whole damned world says and does except the players’ characters.
I got games mixed up. Oops. In any case can you explain what the actual rule differences are that makes it a sandbox? Because yes, I was wrong but your answer answers nothing. Because I could say Zerbert World does X and it's meaningless unless everyone is familiar with the game.