I had to go look – you had me scratching my head!

In the “Replace Text” Shortcuts action, there is placeholder text in a new action to replace `Hello` with `World`. If you leave the second spot blank (as is done in this case to replace things with nothing), the placeholder text remains visible (though dimmed).

So this is a Shortcuts thing, and the true action being taken is to replace a specified bit with null, thereby removing it.

Hope this helps, and thanks for checking it out!