I have menu of toolbars, one of them can be displayed top or bottom (or off).
When it is showing either top or bottom, both the top AND bottom are highlighted in the menu.
I'm not sure it's possible, at least not in any simple way.
The Toolbar command's checked/toggle state will only tell you if the specified toolbar is on or off; it won't care if it's on the top line or not, and only uses that argument to know where to put the toolbar when turning it on.