Server-side mode doesn't do a thing?

I've made a little mod ("code" in imgur photo) that repairs items at the cost of levels, since this is only a command it should be able to run on server-side only, or am I mistaken?

Well if I am correnct in my thinking, it doesn't work, ticking the box to make it server-side only does nothing.

Trying to change or add to the @mod list after or before exporting also does nothing, since if you chance it in Mcreator it just changes it back, and still makes a file saying the mod needs to run on "BOTH" sides, when it should just be the server.

I'm very confused on why it does this and I'm asking for help to find a way to maybe get it to work, I've spend alot of time now just learning it myself since I'm a complete beginner.

Thank you