Zhiyi Zhang (@zhiyi) commented about loader/wine.inf.in:
ErrorControl=1
[ThemeManager] +HKCU,"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize","AppsUseLightTheme",0x10001,0x00000001
You should use 0x10003 instead of 0x10001 because you would want to keep user settings if they are present, for example, after a wine version upgrade.