Mine powered off. I was confused as well but give it a try to see if I did something different to get a power off.
OK, so I tried it and got two different results, based upon how long it was held down.
The first time, I had the screen off. I then pressed and held the power button. Almost immediately, the screen came on, as expected. After three seconds, the home and back buttons began to flash on and off. After seven seconds, I got the message that said to keep holding the power button for 3 (then 2, then 1) second(s) to restart. After it got past that, I continued to hold the power button down. Then, the red LED turned on. When I let go after maybe five more seconds, she was completely shut down, WITHOUT restarting. I then powered it back on.
After waiting for the phone to completely restart (widgets loaded, etc.), I repeated everything from above, but this time, released the power button immediately after the countdown. As advertised, the phone restarted itself almost immediately.
Good to know that you can, indeed, force a power-off, if you needed to.