The fact that the author withheld information from the Apple clerk suggests to me that the author thought the Apple clerk would not understand the “real” reason

The fact that the author withheld information from the Apple clerk suggests to me that the author thought the Apple clerk would not understand the “real” reason why he wanted the smallest box. I believe the author thought the clerk was too stupid to understand the real reason and it would be a waste of time to explain to the clerk why.