Well, it worries me to suggest the answer when so many others say they don't know, but I'll stick my neck out.
The mixture control and throttle don't do the same as on a normally aspirated engine. You will get fuel pumped into the intake even with the throttle closed, and that's what happens when you turn your pump on for a few seconds prior to startup with mixture rich and fuel flow showing.
So when you start the engine you have a liquid fuel in the intake which is all the engine needs to get going, so mixture lean otherwise it will be too rich. When it fires up, and the pool of liquid fuel has been sucked through and used up, you open the mixture and that keeps the engine going.
So that's why I used the word 'essentially', the engine isn't actually flooded in the aspirated sense of the word, but it's the closest analogy I could think of to answer your actual question. You basically have liquid fuel which needs to be got rid of.
Clear as mud? Anybody have a correct answer
