I'm pretty sure there isn't meant to be any air in the cum receptacle at the end. The idea is to pinch the end to remove air and keep it pinched as you roll the condom down the shaft. That way the cum has somewhere to go. If there is air in the tip then when you cum its just going to push your cum down the condom and its a whole lot more messy to clean up. I do agree though that a lot of WLs get this wrong and either leave air in the tip or stretch it too far so that the tip is right against the head.