Some of twitter links when you click them offer "Follow" and some offer "Send follow request"
I get credited only for links which offer "Follow".
Also I think that I would get credits if those whom I sent follow request would accept it!
I think that some users add their twitter links and they ask you to send follow request, but they dont accept you cause they will lose points. Later, maybe they delete their twitter link from fanslave database and then they accept follower without losing points.