Why would Exclusive Modifier get applied to Order Line only upon Order booking to override automatic

I have a situation that is puzzling and am wondering if some Oracle Advanced Pricing gurus can help.

Two modifiers have been defined, one exclusive and the other with non-exclusive setting. The Automatic modifier is being applied on entering the Order line as expected. However, the exclusive modifier is not getting applied upon entering the Order line. The Exclusive modifier gets applied when the Order is booked and overrides / removes the Automatic Modifier. Both modifiers are valid for the line item that I am using for my case, but I am expecting that the Exclusive modifier will override the automatic modifier upon entering the Order Line and not upon Order Booking. How could this be possible if