That's only somewhat true if we are talking about the same sandbox nested (which would be quite dumb to do).
Escaping two different sandboxes are multiple times as hard, and a sane sandbox is not trivially picked, see web browsers and that the fact that the world is not one giant botnet.
Escaping two different sandboxes are multiple times as hard, and a sane sandbox is not trivially picked, see web browsers and that the fact that the world is not one giant botnet.