Maybe because we have some different options in Prefs/GUI ?
As far as i remember (after installing your theme) I manually changed some options, nothing special but it might be the reason of the different behaviour on our systems .. eventually i will post a grab showing what i modified, let me know
P.S.
Your themes are fantastic, in my opinion they are the best themes out there .. maybe not perfect for MUI but almost perfect for the system, my dream is to see AmigaOS 4.2 with a theme like that