He can answer for himself but I think Joe’s response was inside the quote box in blue text - at least that’s what I’m seeing on the old Ipad.
I would also want to see more tests in other calibers before deciding smokeless on top is necessarily better in every instance. I don’t care one way or the other but further testing would tend to yield more accurate conclusions.
The next question is why one is better than the other? I am speculating here but suspect the smokeless just under the projectile gives it one final bump before leaving the barrel. If we could plot a pressure graph, the ignition would show two peaks, with the second lower than the first but still enough for an extra oomph. The mixed powders obviously can’t achieve that, and neither can smokeless under the main charge, because it’s ignited first.