FWIW Dolphin only does it if the filesystem doesn't provide a way to add that metadata directly to the directory and you change the view configuration for that directory away from your standard configuration. Which is how the standard describes to do it. (Some file managers incorrectly add those .directory files to every directory you visit.)

A mac will add a .DS_Store file to any directory just by breathing on it.

[–] ulterno 8 points 1 day ago

Well, those are different specifications. Apple(who wants everything for themselves) vs FDO(whose main goal seems to be interoperability)