It's probably because of the
Lucky Double-Sided Coin trinket. If you get it, you can use the trinket with every set of wolves, and/or every elemental mastery.
I'm not sure if Hooligun's example of saving EM for the 2nd ascendance would still hold true, if you have this trinket, or if it would be better to go ahead and pop EM+trinket, at the 2 min, and 4 min marks, and then at the 6 min mark, they meet up with your 3rd ascendance. I never seem to have time to play with SimC, with my work schedule.
EDIT: For Butcher, specifically, it might be smart to save EM for the 2nd Ascendance, at the 3 min mark, and then pop EM again, at the 5 min mark, if possible (if you opt to use EM over AS).