Possible bug regarding Dungeon Slice sims and Tigers Fury

I recently got a 400 shoulder from the WQ and it had JF and WF on it, (yay me). Anyways, I had a 420 tht just had WF and TC on it, and wondered how closely they simmed and notice something strange.

When simmed, the sim states the TF duration at 72% (I run the Pred talent) however the sim only states the JF duration at 53%? Should this not be equal to the TF uptime under all circumstances or am I misunderstanding something?

edit: for those interested in simming me, I am at trollbane