I wonder if that change is due in part to the change in the buffer zone that effectively shrunk the strike zone. Walks are up and strikeouts are down, and hitters are taking more pitches labeled as being outside the zone and making more contact when they do swing. Launch angle is also down a tick which might explain part of the drop in HR/FB percentage.
If they are making the ball deader, that’s not the worst thing even from the offense’s point of view, since stolen bases and bases taken are up and it’s easier to score runs stringing together hits now than it was before the bases ballooned in size.