Where I live, there is a large bulk gasoline tank farm on the edge of town. I would say it is a safe bet that nearly all of the gas sold in a 50 mile radius, originates right there. That is, outside of a few pumps that claim to have ethanol-free gas at a $1 per gallon premium.
88 (15% ethanol) is largely unheard of in this area. No one has it, at all. Why is that? My guess is because this particular gasoline tank farm doesn't distribute it, and there's not sufficient demand to haul it in from elsewhere.
So, assuming that there isn't anything added to it (e.g. that magical plastic bag of TopTier additives) before it is dumped into gas station XYZ's underground tanks... it is all the same.
And yes, I have a Circle K (a former Mobil station) within 3 blocks of my house. And yes, I was just there this morning... putting gas in the Silverado.