No it does not work like that. If you have it on the 1/2 setting, it should turn on at around 500 watts. But if youre using a 600 watt bulb you will not be using the bulb at its peak efficiency and your spectrum will change from the bulbs specs
So, you're saying that the bulb won't burn because it will only be lit to 500w? Then why is everyone saying it's dangerous?