Bateman has, IIRC, somewhere, maybe even in the material under discussion, written to the effect that there is indeed a superiority to the bipolar of modern construction compared to back-to-back biased ones. He is a careful worker and as well I believe was in the capacitor business for a long time, so he carries a lot more cred with me than some random expert, let alone some loopy audiophool, and especially one hawking his pricey wares.
I know CB's results are counterintuitive. But intuition is not always reliable.
As expressed before I suspect the physics may pertain to reduced or at least different piezoelectric effects.
The effects in any case are small---look at how much trouble Cyril goes to just to get measurements. But then pursuing small effects is fun, if you have the time and inclination.