I'm done with my US flights for this year, so these changes haven't effected me. But I've been thinking about next year...
I normally get oneworld RTW tickets, the "extra" flights within the US are normally on the cheapest available fare buckets that earn points (often O or Q).
I had been avoiding the newish A321T transcons in order to get the 2 class book into A on the DONE3s, but that rule is likely to disappear with these changes. I had also been avoiding booking the QF codeshares, as they booked into D, even on the 2 class flights where the AA code would book into A.
Now that the AA code will book into D on such flights, I guess I no longer need to actively avoid the domestic US 3 class flights or the QF codeshares.
Am I correct in thinking that booking under the QF codeshare in D will earn more SC then booking AA D on the same flight?