I noticed that I cannot even tell that an NSBox is being used on macOS Tahoe when the system is in light mode. The 'box' background can't be seen so it makes it appear that the subviews in the box aren't positioned correctly (because they are inset from the subview outside the box). There is no visual indicator that that subviews inside this box are grouped together because well, you can't see the box at all.
In Interface Builder the box looks fine at Design Time in "Light Mode". In Dark Mode the box looks fine at design time and at run time.
Just figured I'd throw that out there.