Apparently the 3 batter minimum rule is in effect for 2020, but only in the Atlantic League.
The MLBPA does oppose this rule for now, but their approval isn’t necessary.
Notin’s Take: Manfred can implement this on his own, and might very well do so not just to speed up games, but as a bargaining chip for the next CBA, which expires after the 2021 season, I believe...