Here's a video from Tom Wishon furthering our discussion on MOI matching.
One of the interesting things I find is that people will often ask the question "why don't pros do MOI matching if it is so good?"
Having discussed how Tour players fit their clubs with many Tour pros and equipment reps, many of them will grab a dozen or so of the same irons with the same shaft models. So, if a player is using Mizuno MP-4 irons with KBS Tour shafts...they will grab a dozen 4-irons, a dozen 5-irons, a dozen 6-irons, etc. They will try each club out and find the one that they like best and bag it.
With irons like that, the MOI can be much different from club to club. OEM's tend to have a tolerance of +/- 2 grams for head weight from spec. So, if a 6-iron is supposed to be 261 grams, the tolerance can be anywhere from 259 to 263 grams. Similar tolerances can be expected for the shaft. Furthermore, you not only have the weight of the shaft, but how the shaft weight is distributed...so there is a tolerance for how the weight is distributed. Then you have things like differences in how much epoxy, tolerances in ferrule weight...all of which matter (admittedly, less important than head and shaft specs).
A few years ago, I got to measure Sir Nick Faldo's old Mizuno T-Zoid irons. Faldo utilized the same fitting principle of hitting multiple of the same irons and bagging what he liked best. And what was Faldo's MOI for his irons like?
The 3-iron thru 9-iron was exactly the same MOI of 2,750. Only his Pitching Wedge was different at 2,775.
As I've mentioned before, there has been some form of the MOI matching principle prevalent in golf clubs going on for quite some time. In particular, that's why wedges have different swing weights compared to the rest of the irons.
If we look at Titleist, they set their irons at D2 swingweight and their wedges at D5. They know if the wedges were the same swingweight, they would feel way too light. In fact, Callaway is using progressive swingweight with their Apex Pro irons which have long irons at D1, mid irons at D2, short irons at D3 and their wedges at D4.
So, the concept is being used, but not quite to what it needs to be.