I was talking about the MDI windows (those inside the client area, the subwindows), not the toolbar. The MDI windows, regardless of manifest, use the Vista them

I was talking about the MDI windows (those inside the client area, the subwindows), not the toolbar. The MDI windows, regardless of manifest, use the Vista theme since their look hasn't been updated for ~12 years. This is actually something that has been reported to Microsoft before (here is a link for one of the feedback entries linked in one of the issues in the WinFile repository: https://aka.ms/Bjiosw https://aka.ms/Bjiosw ).