Yes I also would have though that JB would be the leader of JJP as well... but like you realised, I just went according to what kprofiles saidWait. JB is the official Leader of JJP and GOT7. He was the leader from the very beginning.
When JY said that he's a leader of JJP he was joking around because YG is JUS2's Leader, so he said that JB has power only in GOT7 (not really XD our poor leader). It's strange that JY is a leader according to Kprofiles
P.S. Leo XD