The Athletic had a story on what's happening here. Not necessarily the Tigers but other teams and pitchers. It's not the signs, but the pitchers tipping the pitch. Usually something subtle in the pitchers movement, his set uo, glove angle or even the way the catcher sets up.
The increasing numbers of cameras around the ballpark and multitude of things like iPads and computers in the dugout or just outside.
The broadcast during game 2 alluded to Naylor closely studying the Tigers pitchers when he wasn't batting, but watching closely. Maybe their not just watching opposing pitchers, but also opposing batters for subtle signs, above and beyond already noted tendencies.
edit, here's the article
https://www.nytimes.com/athletic/6691711/2025/10/06/mlb-pitch-tipping-paranoia-camera-ipads-pitch-clock/
I forget who the Tiger batter was yesterday who grounded out to first base relatively early in the game collided with Naylor during a particularly hard groundout. The batter knocked Naylor's hat off in the process. For a second it looked like there might have been blows.