When is an H ticket, not an H ticket?

Through company policy I have to book tickets with AA - but can use BA as a codeshare. Usually these tickets are the cheapest possible, but occasionally they are booked as an H selling class on AA, which comes through as a BA Y/H, and as such should earn full tier points. On a number flights I have checked beforehand on the BA booking, and sure enough, full tier points come up - 70 for transatlantic and 20 for European short haul. However, the TP are only credited at the discounted rate (35/10). Why?