I came across these videos from the Golf Institute of America
Many golfers understand this, but many golfers did not have any idea on the subject. Years ago I had a Callaway War Bird Driver and 3-wood. Loved the 3-wood, struggled badly with the driver. Eventually we had the shafts measured and the 3-wood was X-Stiff like it was marked, but the Driver was a Ladies Stiff shaft. I then measured my Taylor Made irons which had Dynamic Gold shafts and the X100 shafts were fine except for the 9-iron and PW which measured about at a R300.
Currently, I play with some Rifle FCM Shafts that are 'Frequency Matched' and are supposed to have low tolerances. About 10 years ago I played with some FCM steel shafts and to their credit, they were all very consistent in shaft flex. It's just the shaft flex was stiffer than a tire iron.
Graphite shafts are wildly unpredictable. And yes, you had better check out lie angles, lofts, etc. if you are buying any club from an OEM.
You're best off finding some type of clubfitter and always trying out the club before purchasing it, making sure it fits you and then making sure the club meets the specifications it has marked down. American Golf Institute isn't discovering anything new here, but it's very important for golfers to take notice.