Seriously?? What is the problem in scanning it for a second time anyway?
Presumably you two are the classic type that think the handbaggage rules apply to everyone but you as well?
The problem is that HAL use the time from the first scan to the second scan to show the CAA that processing times are low and thus justify their understaffing.
Not sure how this relates to hang baggage but I personally stick to the rules as far as I am aware.