Why does an "Initializing World" Message appear when I change a USF file?

This is more of an annoyance than anything else, but here goes:

I’m using an USF file to implement a compute shader. If I apply changes to it and recompile shaders while in the editor (by pressing Ctrl+Shift+.), it takes no time at all and there’s a good workflow.

However, if I DON’T have the editor open and apply a change to the shader code, when I open the editor I’m welcomed by an “Initializing World” message (attached image 1) for quite some time (~1-2 minutes). Checking the task manager I notice that there are shader compilers running (attached image 2), so I’m assuming it’s compiling a whole lot of shaders it needs.

What’s the main difference between having the editor opened or closed that triggers this effect? Also, is there some kind of solution?

I would really prefer being able to make changes without the need of remembering to have the editor opened all the time. Anyway, as I said, its really just an annoyance right now.

Thanks in advance!