I don't think this actually reflects the new light/dark mode people are referring to here. It will most likely always be the default theme - light.
Also changing those old themes has a good chance to "break" any (poorly made) apps doing their own themes. You could change some colors in the palette and parts of the UI could end up being difficult or impossible to read. Happens if the app uses a combination of palette controlled colors and custom colors.
Correct. For Win32 apps, the only official support for dark mode is some WinRT APIs to tell if it’s enabled, so you can “adjust your application's painting and rendering code to use a Dark mode color set”
> Also changing those old themes has a good chance to "break" any (poorly made) apps doing their own themes.
They already do this. COLOR_3DFACE has gotten brighter with each successive version of Windows and in Windows 11 is #F0F0F0. I've had to fix UIs that became unreadable as a result.
Also changing those old themes has a good chance to "break" any (poorly made) apps doing their own themes. You could change some colors in the palette and parts of the UI could end up being difficult or impossible to read. Happens if the app uses a combination of palette controlled colors and custom colors.