I don't adjust the tilt either. Even if the bike is tilted up slightly, my body position relative to all portions of my bike will still be the same as if I was level. Does that make sense?

Basically, even if I'm tilted up, the relationships of my legs to my pedals and my arms to my handlebars are the same. Everything on the bike is tilted up. If you alter the tilt of your saddle and keep everything else the same, isn't that ultimately affecting your fit overall?

There are people on this board, however, with far more knowledge about these things than I and so I will happily defer to them.