Admin commands executed by command blocks are not logged when the gamerule logAdminCommands is set to true unless the gamerule commandBlockOutput is also set to true.
In 1.12 these two gamerules had nothing to do with each other. With logAdminCommands set to true all commands were logged in the log file and with commandBlockOutput all commands were logged in the game chat.
Now it does not seem to be possible to log commands without spamming the in game chat.
We need this because we listen to changes in the minecraft log file in order to trigger an external program from within minecraft: https://github.com/Energyxxer/Vanilla-Injection