The pause button is bound to the wrong key. It is bound to the physical escape key and not the escape key set in the keyboard layout. This is not possible on Windows, but is on Linux and *BSD. This is on X11 as (AFAIK) Java still does not support wayland and runs through xwayland.

Demonstration:

https://youtu.be/FLu41laUXew

To reproduce:

Install Minecraft on a *nix machine running X (and not wayland)

Run the following command to set the option to swap caps and escape:

$ setxkbmap -option caps:swapescape

Launch Minecraft

The game will now still pause when you hit the key labelled escape rather than the key that the rest of the system treats as escape. It will also toggle caps lock.