That's one way of doing it, and generally makes for a better end user experience since people can see that the charger is down and not bother with it.
On the other hand, I read somewhere around here (possibly speculation, possibly based on a real conversation with someone at Tesla) that Tesla can compare button clicks on the charge handle (to open the charge port) with successful charging sessions. Superchargers and the cars are sophisticated enough to self-report errors, which might garner Tesla's attention more quickly than a stall that hasn't been used in a while, especially at stations with lower utilization.
So I'm torn on what to do. Toss the handle over the stall or let people figure it out on their own.