Incorrect. If F is full, the service you will receive is less and slower as if F is not full.
To be honest, I tend to believe the regular F flyers on here rather than somebody who just says "Incorrect". I'm not a regular F flyer, but I've done full and empty sectors and haven't noticed any difference. I tend to eat in the lounge first and then on the plane after around 4 hours, and I've never had an issue getting my first choice.