There's some timing rules when a model dies. Being 'boxed' is one of those steps. It goes disabled -> boxed -> destroyed. There are effects that could trigger at each of those steps.
For instance, you make tough rolls at the disabled step. If you heal the point there, you never get to boxed so Snacking never triggers. Other effects could remove a model from play after being disabled, so those would never get to boxed either.
In most cases, a model just dies and you don't have to worry about the timing issues.
