I am expecting a BA dual inventory fare to post the TP and Avios of the higher cabin. Assuming they do, then it seems entirely inconsistent for AA dual inventory fares not to post the same.

Is there some underlying confusion here between a dual inventory fare with a higher cabin at the time of sale, and an airport "promotional upgrade" on AA, which indeed does not credit the higher cabin?

Might it be worth starting to ask BA for credit for the higher cabin of a Dual Inventory Fare, pointing out is not a promotional upgrade purchased later?