I prefer the grey, because of things that can affect the user experience, like ghosting with pure black. Typically, the grey won't appear to ghost, while pure black will with scrolling/animations.

Full black is rough for reading text in my opinion. It also seems it might be subjectively harder to focus on pure black backgrounds for those with stronger astigmatisms.

I think an option for both could work. Maybe a new settings option to choose between dark and black for dark mode. Or an on/off switch to enable pure black in dark mode