I believe the gains are real, just not your explanation of the reason behind it. Case shape does not change the bolt thrust; that's made up by people who don't understand how pressure works. If the case body sticking to the chamber walls really reduced bolt thrust, you'd have a much higher chance of case head separations with an AI chamber. It doesn't work that way.
Like I said, the difference in the throat does a lot more to account for any significant gains.
