So revisiting this, I recently filled up the edge with E85 and 87 octane because the gas station was out of 93. So to make up for the lower octane fuel, I added a gallon of E85 on top of what my calculations were to fill up the tank (I think it was supposed to be 9 gal E85 and 4 gal 87, so instead I did 10:3). Based on our conversation I assumed my vehicle would pull timing and be slower due to the decreased octane used, so my preconceived notions going into this was that it would "feel" slower. But it turns out the opposite was the case. The car felt faster and felt like it pulled harder. This is likely due to the increased ethanol content.
Does the octane of the fuel make a difference in how much timing advance there is in an ethanol tune? sure. But as the concentration of ethanol goes up, the octane of the fuel used to mix becomes more and more negligible.
If you're fine tuning a pure drag car, sure the octane is likely very important, but for an ethanol tuned DD, I find it hard to believe that fuel octane matters, at least on an E50 tune. Maybe and E30 the octane of the gasoline is a much bigger deal, but not so much on a powerful, but conservatively tuned E50 DD.