Interesting results in that video.
I'm going to have to do some testing of my own again.
Back in the day when I used a flame to anneal, I got some cases that had lost all memory and it was like playdoh. When I seated a bullet, I could pull it right out, no matter how small the bushing I used. The brass lost all memory.
So how does Cortina get different results? I'm thinking either the seating pressure remains similar because of the force to expand the neck, but actual tension must be different because of different spring back, or something else entirely. Hard to believe they are all the same.
