That doesn't say anything about which seats will be on the 789. Note that after the installed slimlines in the 320, pitch in E+ is measured at 35 inches, exactly the same as on the 789. Note also that slimlines are not just about capacity, but weight savings as well.
In any event, I assume we'll find out soon enough which seats they're using. Hoping that someone here in the forum has that information . . . .