I think I figured this one out on my own: If you hover the mouse over the center of the screen, the "unit picture" of the unit activated by the "Find Idle" key will show its current orders. If those orders are "Awaiting Orders" that's a unit that needs move orders.
Just gotta keep the mouse pointer centered in just the right spot and it all works out. Hit 'Tab', center the mouse, then hit 'Tab' again to cycle through everyone. Units occupying the same space as other units but not in a stack will automatically be brought to the foreground by the "Find Idle Units" command, which is kind of a nice touch.
The "unit picture" is over on the right. If anyone else had the same problem I did, I'm glad I could help.