I think he has a point though. The 5 minute reset timer made sense when DSEs were limited to 20 people. Now that it's limited to 5, I think the reset timer should be cut down to 3 minutes. The problem with a 5 minute wait now is that most people do exactly as you all suggest and change instances. But now that there are dozens and dozens of instances, there's no guarantee anybody will be left when the timer is reset.
I also think the OP is pointing out that when the first person enters the instance, it's automatically reset, so they have to wait 5 minutes regardless. So unless there's always someone in an instance, the first person will cause it to start counting down from 5.