Light Groups compositing

I just started using Light Groups and have one question about compositing them properly.
I made naive assumption that the beauty image will be identical to all light groups added together with Mix node (Add).

But it’s not the case.

Image made with adding LG have much more contrast, to the point that some parts are burned or filled with almost black or solid black. This is true for comping the same light group passes in Blender and in Krita.

What is the proper way of comping Light Groups so the outcome is identical to the combined image?

Can you attach a small representative .blend file which demonstrates your issue?