As a former catcher I can say that the pitchers and I would get in a rhythm and what I called, they would throw, because it was the right pitch. Lol.
But, knowing that to be the case, I'd throw down the "hang loose" sign- which was our shakeoff sign- a time or two before giving my actual sign.
Keeps the hitter on their toes.
Now that was legion ball, this is MLB, so I'm not saying that's what's going on in Zunino's starts with Paxton and Kuma. Buuuuut I'd be curious to see what the center field camera has to say about it...
Despite the shaking off of signs, the pitcher/catcher relationship doesn't seem to be strained or lacking at all.
On the contrary. These guys have come in with a plan and executed.
So, based on that, along the results (proof is in the pudding), my best guess would be, "It's premeditated Partna". Zunino's firing off a couple blanks to get in hitters head. And they're running off the field while we're scratching our heads about how Iwakuma just snuck a 90mph fastball past the hitter.