The attractive LTR certainly produces the effect of instant friendships, but the times are random and not all that frequent in my experience. However, once charism is supermaxed, the sim will regularly get instant best friends. My current sim (week 2 day 3) has 37 best friends.
But, I got the impression that Sadsim had a very new sim and that the instant friends were mostly happening at a particular time (11pm.). I don't have season's, so don't know how the Online dating works. But, if the friends are already made and charisma has been maxed and he has the attractive LTR the sim will continue to get new friends instantly.
I find this annoying occassionally, it makes completing the photographing strangers challenge impossible. You try to photograph a sim you have never met and you find its a photograph of "one of your friends".
Other things which seem to affect this instant friendship affect are the "eye candy" LTR, the "friendly trait" and the "beauty" wish from "dusty old lamp". I don't know if their are others.
