Some wine bottles actually have a place on the bottom that you can stick your thumb into, it's called the "punt". The guy in this pic does not use the punt but if you go to a fancy restaurant, there's a big chance you'll see someone holding the bottle like this when they pour wine, holding the bottom:
It's considered to be the correct way to pour wine and be fancy.
Here is a pic of someone with their thumb in the punt:
That could be what is going on in your advertisement picture. Or it could be a photoshop fail.
I just wanted to mention the wine bottle punt and how to pour wine the fancy way. When you are good at it, you make it look effortlessly and smooth. When you are bad at it, you make a huge mess. Wine and broken glass everywhere.