It's one of teh ways that clubs can be "fitted" - rather than swing weight, MOI etc
Have been around as an idea for quite a few years
There's defintely something to the idea as it works to the idea that all the clubs are as easy to swing as your 7 iron. Does make little wedge shots fun Shoudl be good for accuracy although distance gaps might not be as big as normally ?
I wrote an article concerning the reason behind varying club lengths. You can click on the following link if you would care to read it: Different Club Lengths