The default placeholders for the TPS is not reporting the correct values.
Reproducing:
- Install the following mods:
- Configure player list to show both the TPS.
- Execute
/tabtps toggle actionbar to display actual tps on the action bar.
- Start chunky pregenerator.
- Watch TPS
Displayed TPS is incorrect:

Correct TPS:

During both screenshots, a chunky pregeneration task is being executed, which consumes the server's CPU for generating chunks. The low tps of about 5 is also observed in game.