Based on that article, it sounds like the combination of multi-player and turn-based combat creates the problem for day/night timing. It sort of sounds like the same problem people had with Time Stop in multi-player.

I have no intention of ever using multi-player with BG III.

If we can't get the diurnal cycle, then I propose we see Baldur's Gate city only at night ... perhaps around the winter solstice time, when people decorate their windows and pine trees with tiny colored lights. Magical.