I think I have to disagree with this statement on 4/5 for low cappers and 3 for high cappers. Low cappers have the "feel" or "touch" to control distance much better than high handicappers plus are less likely to need them. A few years ago when I started carrying all these wedges I found it very comforting to know that if I was 40 yards out, I brought the 56 degree wedge back to belt high and swung through to belt high. 50 yards, same swing 52 degree. 30 yards, same swing 60 degree. 60 yards, same swing with a PW or 60 degree from shoulder high, and so on. I went so far as to write down the distances on a card and carried in my bag. I would get to the ball, determine the distance, look at the card and I knew exactly how to play it. It makes all the difference in the world to have no doubt in your mind how to play the next shot. The interesting thing about it is, as I got better at making contact with the center of the club face, I saw these distances grow to the point where I needed to add the 64 degree wedge.
High cappers are much more likely to miss the green or be in the 30 to 50 yards from the green range than low cappers. Having a go to shot from these distances is very important. Having a selection of wedges and know how hard to hit them makes it easier. The likelihood of hitting the green from 200 yards is slim, but the likelihood of being inside of 50 yards from there is high. More wedges give increase the chance of getting up and down.
Totally agree with you on this. I recommend that high handicap players have as many wedges as they can carry because it gives them more "full swing" yardages. While I wouldn't advise a high handicapper to try to figure out their 25%, 50%, 66.66%..... shots (I'm exaggerating, obviously), I would recommend learning a half shot with all their wedges (if not all irons). This is a shot I've had since I was trying to break 100 and it's one of my favorites. I find that even now, as a "better" player, I would rather hit that half shot hard from 60, 70, or 80 yards than try to finesse a wedge in from 30.