i was just thinking, i have another idea on why it does that or aids the effect of the suction, you use warm water to activate the yeast fermentation process. well for the short time that u you fill the bottle up with warm water the air expands pushing excess air, giving a short bubbling period before the air cools, then causing a reverse of air pressure in the bottle, causing a suction until Co2 can replace the deminished supply of gas forced out of the bottle. This may be a big factor or little factor to this problem, i dunno? yeast works really fast so it may just cancel out the whole effect all together. also while the water is warm, evaportion takes place causing th air pressure to climb even more.
This is my 2 3/4 cents