Old old Windows Forms had its own text rendering (and still has), but most controls now have a second code path that uses the system's text renderer, which got

Old old Windows Forms had its own text rendering (and still has), but most controls now have a second code path that uses the system's text renderer, which got updated with better shaping, more scripts, etc., while GDI+ basically never got any updates. You can see that when there's a call to SetCompatibleTextRendering(false) in the code somewhere; then it's using GDI instead of GDI+.