Is it possible for the randomness to be more heavily weighted towards the larger activity requirement? (Then it wouldn't really be "random" though...)
Eh what?
I believe he's asking if the site is more likely to wait for a higher activity number before rewarding Legendary. The answer is no; it's 100% random between the two set points. Due to people's luck and the nature of the activity system it can look like it does lean more heavily to the higher side, though it doesn't.