I guess you're right. I was thinking along the lines of "a less common pattern is less likely to be noticed and tried correctly the first time around and by the

I guess you're right. I was thinking along the lines of "a less common pattern is less likely to be noticed and tried correctly the first time around and by then the traces left of it are ruined" but now that I've looked at the photo again I see this is probably wrong. On a phone like that any grease pattern should be pretty obvious.