Jim:
Doing the numbers:
6' in 1:22.5 scale is 3.20"
6' in 1:20.32 scale is 3.54"
Difference is .34" or about 11/32", closer to 3/8" than 1/4".
Remember that on a 3D model you are looking at the volume of the object which makes things appear significantly larger than the linear dimension differences would imply. The fact is, 1:22.5 figures, when used in the foreground, look pretty wimpy alongside 1:20 figures or other 1:20 scale items such as doors.
Using those same 1:22.5 scale figures a little further away and not next to 1:20 scale items can actually provide a forced perspective, helping enlarge the scene.
Happy RRing,
Jerry