3DMark just takes a snapshot of the speed at random, so it's liable to show anything.
Seriously, you haven't seen other people's 3DMark scores with their CPU's basically at idle? Happens more times than not. If their CPU's show max speed, they were probably using the High Performance power plan instead of Balanced (or whatever it might be set to, otherwise).
You're fine. No worries.
Edit: Never mind the fact that your score was one of the best in its class...