While I like the idea of folks selfishly taking up supercharger stalls and not even plugging in, I'm not sure how I feel about what is in essence touching someone else's property.
I've argued against unplugging people who are at chargers for a long time, as you don't know what their needs are.
It's a bit harder to justify anybody parking at a supercharger and not plugging in as anything other than forgetful or selfish...
Hmmm....
That's why I like the current way it's set up. If you're charging and locked, then the port is locked too and no one can pull out the Supercharging cable. The idle fees are "punishment" for taking up the spot when you can't charge anymore.
However, it's unlocked, so someone can plug an inconsiderate driver in (how can that damage anything?) and so you're "playing by the rules" and subject to idle fees. If you're low on battery, you get juice. If you didn't need juice, you're subject to idle fees.
Either way, a notice will pop up on your app telling you to basically move your car if you don't want idle fees.