John,
That Pelz chart is for Tour players, who always make solid contact (hence, good distance control) but are just as subject (hey, maybe more, given their swing speeds) to torque, getting clubface square at impact, etc. as average golfers.
If you look at the USGA slope rating guide, you will see that the shot dispersion pattern for 20 handicappers is quite different. They require just slightly more width than scratch players, but they also require much greater depth (about 1.5 times) to stop their shots, on account of poor contact, less backspin, etc.
Generally, I am designing greens to accomodate the shots of average players. As such, I often design the green to be (as per USGA charts) 15% and 22.5% of the approach shot length I anticipate after a well struck tee shot of a 20 handicapper, playing from a tee that gets them to the first landing area. As Tom Doak points out in his book, its impossible to figure just where "the average player" will actually be approaching a green from, so I don't obsess about hitting any width or depth precisely.
However, its a good place to start as a reality check, and as such, most of my greens with an anticpated 160 yard approach gets a green approx. 24 yards wide and 36 yards deep, plus or minus. I adjust for prevailing winds, difficulty of hazards, slopes in landing areas, strategies, etc. (For example, if there is a downhill lie in the landing area, I probably will increase the depth of the green knowing that those shots are likely to come out lower than normal and with less backspin)
I also try to vary the greens so that some approach shots are more difficult than average, and others less difficult. As Mike Hurdzan pointed out in his book, if all greens followed the USGA slope guide for sizing, then each approach shot would have exactly the same degree of difficulty, or shot value.
For example, I favor downsizing greens on the longest par 3 and 4 holes to test scratch players accuracy with longer clubs on the assumption that average players are approaching the green on the 2nd/3rd shot with a wedge. Hopefully, they have read Pelz book, too, because the 66% green size for a scratch players 200 yard approach is wider than it it long, again because of their distance control.
Anyway, that is one gca opinion on how actual shot data from Pelz and the USGA can affect green size. If you asked from the superintendents perspective, I would also note that greens can be too narrow - specifically greens that are less than about 45 feet wide or deep often don't allow them the necessary room to move pins from left to right/front to back, and worn spots result.
We have to figure that into green shape decisions, as well.