@jackie_w: Ah, that's because overlay (in MiniClock) switches to hardware inversion (while, usually, we go with simply inverting the colors ourselves

[And I do mean inverting the colors, and not swapping bg for fg]).
AFAICT, software inversion *should* do the trick for plain bgless, though. I'll double-check, as it's entirely plausible that this is yet another thing that's subtly broken in the OT codepath ;p.
EDIT: Ah, yeah, I see what you mean, bgless definitely ought to switch to true nightmode on its own, too

.