To me from the outside it seems like both with Gio and Rey, they simplified their offerings, staying mostly fastball to get them set, and as the season has moved on they have opened them more and more with the offspeed stuff. Almost like instead of everything at once, they were going one at a time. With Gio it seems like even velocity was added back later, my guess is to attempt to get rework his wind up and motion.
I could be totally wrong, but that is what I see. If you think back to Sale, it was kind of the same thing. They held off on the slider for the most part early on.