I think there’s a professional courtesy issue at hand here, in which all teams freely use the cards and no teams want their use of them to be questioned or put in danger, so they allow each other to use them without publicly threatening to undermine the practice. This may exist in the same vein as sticky substances or spider tack earlier this year: managers were loathe to call other teams on its use because their own pitchers used it to good effect. Professional courtesy.
There may also be the very public act of Kiermaier picking it up and simply walking back to his own dugout with it. He publicly disrespected the Jays when he did that. That’s the kind of thing that just doesn’t go unpunished.
I would like it if the incident were to spur a discussion inside The Game about whether the use of cards during play should even be appropriate, and whether they should move to a sort of “Amish baseball”, in which all the technology you want to use is fine while prepping for the game, but once you cross the white lines, no cards, no tablets, no smartwatches, nothing but printouts in the dugout. Maybe make players actually memorize tendencies about the other team while they are out on the field. Wouldn’t that be a kick.