What does this mean? "Why not just put duplicate files in each folder (as an alternative)? "

I love tips like this, but I don't get it. Things change, you are always coming up with better titles for folders, better organization technique, always de-cluttering and trimming.

And.. Spotlight cannot follow this? It's index is static?? It does not pickup new changes..? And it does not know where new files and folders are after the index is made? I thought it was dynamic, it's not?