Not even close.
Shot size and velocity are TWO different variables.
In general, large shot shoots tighter than small shot.
In general, low velocity = tighter patterns. It's a shot deformation issue.
The biggest single variable is shot hardness, followed by shotcup effectiveness, followed by velocity. You need to investigate this for each shot size to have any meaningful data.
The single tightest shooting 20 gauge load I've seen was Federal 'Field and Range' circa late 90's in shot size #8. It turned any open choke gun into at least 70%, and maybe more. It was a fast load of #8, but the shot was exceedingly hard - harder than bagged STS shot or bagged West Coast shot. Man, it was hard.
