I know what you mean about never seeing one before, my best friend gave it to me as part of my baby shower gift. I believe it is called an anatomic nipple it is meant to be that way so that it fits better in the newborns mouth and they can latch on better.
i dont know if it has anything to do with it, but my wife says the webbing helps the nipple collapse a little bit because of the fact that air is not in the bottle or if done properly is not being introduced by the infant. it is like when you gulp down a water bottle how it is hard to suck the last bit because you are not introducing air to the water and the bottle starts collapsing to help. a baby bottle can not collapse so they put the collapse in the nipple.
its no problem at all although now that I think about it I should be trying to up MY chances of winning lol I desperately need baby stuff seeing as my boyfriend and I are just starting out in our own place and all the expenses leave very little left for food and baby things. but I'll definitely give it all I can to try and win this bottle since my little one is growing up way too quickly lol wish me luck C: