First: I do the 1 round per load increment thing to establish pressure indications and get a feel for velocity. Much more economical to make 10 rounds at 1 each for .3 or .5 grain increments than to make 100 rounds at 10 each and waste those that are no where near the expected or desired velocities. I chron 'em and then I graph the results, I believe the "node" are visible by the predicable increment in velocity just prior to a reduction in the increment or even a reduction in velocity. Explained, If a few loads in the ladder show a 50fps per increment increase in velocity but suddenly drops to say 10fps or even back slides for a couple increments then for me, there seems to be a node at the "peak". Not enough data to make this a method but it helps me keep the round count down during load development.
I don't have my data book or I would enter a real example to express the above.
Second: didn't you mean increasing seating depth reduces case capacity and increases velocity?
FWIW: My A-Maxes and V-Maxes all like to be -.005 to -.010 from the lands but WMMV.
The longer the COL, the more case capacity you have. In effect you can put more powder in and get more velocity.