Isn't the box scenario a rather pointless argument?
What does the "hide" action get you when you're in the box?
You're already unseen and your location is known since your opponent saw you entering the box. You can become unheard and I suppose otherwise undetectable, but how does that affect how the situation plays out?
1. The creature in the box is not hidden: the opponent walks over, opens the box and attacks the creature.
2. The creature in the box is hidden (unseen and unheard): the opponent walks over, opens the box and attacks the creature because it's easy to guess their location.
If the area that is being hidden in offers only a single location to do so, then hiding your position while being observed is futile.
So what about secret exits from the box, such as a secret trap door or a teleport? You're still looking a mostly useless hiding roll. Why hide and teleport? The effect is almost always the same either way--your opponent no longer detects you.
The only times I can think it would be helpful would be these:
1. You want your opponent to think you are still in the box, drawn them in to attack it while you teleport behind them and attack them instead. Theoretically, the hiding would allow you to teleport and secretly appear behind them.
2. There is a secret exit out of the box but its operation is noisy enough to warrant a stealth check to use it in secret. Perhaps you want your opponent to think you are still in the box or you just want to confuse the situation until they find the secret exit on their own.
Either way, you are expanding the size of the hiding location from a single position (the box) to something larger wherein your true location can be lost, thereby allowing a stealth check to do so. Its the same as if you had entered a far larger zone of concealment to begin with.