I generally carry nothing in my bag that I need to take out but the odd time I have the lap top in there, I always step to one side and do the deed in the bench area, whilst keeping the rollers free. I am considering reviewing this consideration as I'm noticing others who grab a tray, push past, get to within a couple of metres of the Xray, then commence to unpack. I go from being at the head of the queue, to being four back, standing watching them going through a far more complicated unpacking routine.
To me, the courteous thing to do is sort yourself out some distance from the Xray and let those who are already sorted, pass through in an efficient manner. If you do not, surely you are being rude, not the person who is ready to go and walks around you?