F3 Screen Mob Cap Counter Only Displays on Singleplayer

The new Mob Cap counter that was added to the F3 screen in 20w18a only works on single player mode.

What I expected to happen was...:
The Mob Cap counter would appear on the F3 screen when playing on a server.

What actually happened was...:
The line was missing from the F3 screen, even if the player is an operator.

Steps to Reproduce:
1. Load up a singleplayer world

2. Press F3

3. See the line starting with "SC: "

4. Join a multiplayer server

5. Press F3

6. See that the line from step three does not appear, even if the player is an operator