Ok, so I found this article about Patton Kizzire winning at the OHL Classic at Mayokoba and it has a WITB section because, well, Titleist is trying to sell clubs.
I also found a page with the specs for the 718 irons...
My questions is this... why if you're using the 718T-MB in the 4i would you switch to the CB for the 5&6, then back to a MB for the 7-PW?
It seems to me the T-MB has been designed as an "easy to hit" long iron and they continued that on down to the shorter irons. I'm sure there are feel differences between the T-MB and MB which could easily explain the move from T-MB to MB, but if the 4i is easier to hit in the T-MB than the CB, then why would that be different for the 5&6?