not just that, the networks has like a statistical model to access whether your leads are real or not. If only 2% go to the second page, it means your leads are shit, and they might just ban you or withdraw the commission.
If you pass the first round, with say 50% of your leads going beyond the 3rd page, they will then see how your leads convert at the back end.
They will email your leads and see open rates, response rates, etc. If your leads never open the emails they sent, consider yourself screwed. I spoke to the director of one network, and this what I got from the conversation. If you're getting away with fake leads, its just either luck, the network is stupid, or they are going to end the campaigns soon when they see the leads are just shit...