I'll take a stab at this. Many times "A or B" are used when they are different in some way, but both have something in common. For example, an alternative to driving to work is to bike or walk. It's cold out side, so I need a jacket or sweater. Can you call or email me when you get the results. In all these cases, the A or B construct is used to tie together items that share something (alternatives to driving, cold-weather add on clothing, and methods of communication, in these three cases).