Intentional a 2 min penalty for delay of game, unintentional there's no line change. Every puck clear since the rule has been instituted has been unintentional.
This isn't like a high stick where someone could get hurt, it's like a missed pass that turns into an icing. And there can be caveats with the rule, if no pressure from forechecker and the puck bounces and goes out... penalty, if there's pressure and it goes out and it's pretty clear the defender wasn't trying to flip it out, Face off and no change. An accidentally on purpose flip out is so obvious, an unintentional act is also obvious. Teams shouldn't be punished for accidental acts like this that don't cause bodily harm.