My thoughts are it has something to do with this:
https://www.batterypower.com/2025/7/1/24459491/atlanta-braves-analysis-offense-lineup-aggressiveness
The new hitting coach is teaching a more patient approach, and some of the players following that approach are not better for it. If that's the case, it should be up to him to realize that and adjust the approach to fit the player...especially someone as completely lost as Harris.
This also got me thinking about why the offense tended to be so feast or famine in the past. If the approach of the entire offense is "guess what pitch is coming and hammer mistakes", then when they come across a pitcher who isn't executing or isn't prepared to exploit the hitters' aggression, the Braves offense opens a 2023-style can of whoop-ass on them. However, when a pitcher is executing, and is exploiting that aggressiveness, the offense vanishes because there are fewer mistakes to guess right on and punish. Since those types of games tend to be pitched more often in October, the Braves "guess and destroy mistakes" offense is easier to silence. As the league has understood more about their approach, they have learned to use that aggressiveness against them since 2023.
Someone has been saying it for a while..."the league adjusted to these hitters and they haven't been able to adjust back".
So the plan was to teach the Braves hitters to hit less like cavemen with clubs, and more like Chipper Jones..."professional hitters". Problem is, most of these guys aren't taking to that approach well at all, and the result is a lineup that can't even punish mistakes like they used to. The Hyers experiment was likely doomed based on the skillsets of the hitters on the roster.