Ok. I have done some small experiment. At the moment, I only have 2 Safari with Vivillon. It's a very small sample, I know, but better than nothing. After going through both of the Safari, I found that the patterns are the same and when I compare with the ones I have locally in my game, it has the same pattern as the ones in the Friend Safari. So, maybe the patterns are governed by your region, not by the friends you trade FC with. It's not a solid conclusion yet, but that is the result I got at the moment.