Having turned on the dark mode, i found one file display changed correctly, the other one with only changed font colors, but persistent backround image. The file display with the proper dark mode has its image from Prefs PAGE="images", while the odd one comes from Prefs PAGE="folderimages".
They are different backround images. Now i don't know, if this is by design, but since one background image is overridden by the dark mode, i'd expect the other one to behave the same way.