Hmmmm...that is a very interesting insight. I had never considered that. All of the pumps in my area indicate "pump may dispense E-10" and I assume they do but it is hard to be certain.
What is the reference for this table? The numbers do make sense, so I am not really questioning this, but am curious as to how reliable the source is.
Given the uncertainty on what you are getting from the pump, what do you do? Tune for somewhere in-between (E-5)?
It seems this would also be a problem for production cars, unless they had some fairly accurate way to determine the mix of the fuel. I know there are "FlexFuel" vehicles that can handle different fuels on the fly but I don't know the technique to do that. It is likely easier to distinguish between gas and E-85 than gas and E-10.
I know some people complain of how their motor runs on E-10, and in essence the tune may be leaner with the E-10. I still feel the proof of the ideal WOT AFR is going to be on the strip or a dyno, not one specific number.
