FPS Increase while recording

I was testing out Gothic 3 on my laptop. It was lagging horribly. I thought just to see how bad the lag could get, I decided to record Gothic 3. Then something truly strange happened. I got and FPS increase. What? Why didn't they just give me the increase in the first place? I think I've just discovered a major flaw in Direct X games. They never live up to their max FPS when they could, easily!