Oh, I did that and a bit more and the pictures certainly don't answer my question at all.
Brent, the bore size isn't much of a factor, within limits. The convergent constriction causes the pellets to accelerate as they pass through. The only energy available to support acceleration is contained in the internal pressure of the shot column (air pressure and pellet to pellet contact pressure stored up from the trip down the barrel). If mass flow rate is not maintained, we have a "restriction" (as opposed to a constriction) and the barrel blows due to increased pressure. Failure to maintain mass flow rate occurs with shot bridging and obstructions.
During choke constriction passage, the pellets are rearranging themselves further forward, which means higher velocity. The instantaneous velocity and directions at muzzle exit (forward and sideways) predict the ballistic trajectory for flight in a zero gravity vacuum. Aerodynamic forces and gravity alter said trajectory in reality.
Zero choke (cyl bore) pellets do not experience the acceleration and pressure drop as above. Therefore, the front row of pellets are encountering aerodynamic drag while the trailing pellets are still at muzzle velocity. The cyl load experiences considerable pellet to pellet jostling at muzzle exit. Sideways velocities gained from this jostling will remain with the pellets all the way out.
Note that the muzzle diameter does not play into the above explanation. The factor is amount of constriction. While we state choke in diameter reduction, the real effect comes from bore area reduction. It isn't quite that simple because the area reduction must be at or near the muzzle. In a parallel bore, the wall drag will reduce velocity which will rebuild internal pressure. If the foregoing were not so, we could establish choke with the forcing cone.
Does that help. BTW, you have to think in fluid flow, not in simple mechanics.
DDA
