I think this is one of those things that "isn't really proven" because it's obvious to the ones who do it, and the ones who don't feel better pushing the idea it's not proven.

I'm a very scientifically minded person, but I'm old enough to be able to confidently make my own decisions in some situations where "it isn't really proven".

Tell you what, stop flossing. When you get a really bad breath floss, and smell the bits that you find between your teeth. That's what rotting food smells like. Now, if I don't want rotting food in my living room, I certainly don't want it inside my mouth. I don't really need a scientist to make the call for me here.