if there in no water introduced to the ethanol blended gas, there would Not be a phase seperation, that was not the problem in the tank that adressed in this post, even the underground tanks at the filling stations are vented.
Ethanol has some issue with the early production seals and gaskets not designed for the ethanol, it does act as a drying agent for rubber and some gaskets, plastic tanks, etc, but most of this stuff has been generated to accept the ethanol, but if you don't introduce water to it, it don't seperate.
It's been a problem for yard equip, small motors, and such in the past, but like Doran said, it's been around a long time, not so much a problem any more, think Alcohol, we have all put tha in our tanks to absorb water.
The water seperating gas filters we have today, on our boats, are great, OEM, they have a shield kinda like a chamois skin inside then, water will absorb into the shield, but gas will pass thru it, when the shield is totally absorbed, it stops the gas from entering the carb, kinda neat, but some of the aftermarket filters don't function like that. Gasoline will run right through a chamios skin we dry our cars and boats with, but water will not, it absorbs that, like the water seperation gas filters do.