22 points
Yes, because full black/white contrast is harsher on the eyes than a dark grey with white or light-grey text. For power/efficiency, black pixels definitely makes sense, but concerning user experience and eye strain, there are many good reasons certain color palettes are used.
14 points
Obviously not every single OLED panel can be tested for this if the manufacturers don’t do it themselves, but a few places tested OLED/AMOLED phones and found slate grey is close enough to full black in power savings. Since then I just choose the most visually pleasing theme as some full black themes are really poorly designed.
2 points