devtrackers.gg
The brush could be any follower and the opponent doesn't have to commit to anything other than the 2 mana. You're thinking that you're gonna mystic shot a brush and kill nidalee, but you don't know that. It could be anything, and even if it's something like the overwhelm, you're still only trading 2 mana and 1 card each, and mystic shot is a really important card to take away. And the opponent has the choice of whether they want to save the brush or not, they could let it die if it's not important, or spend the 1 mana card to try to save it or be mana positive if you spend another removal.
Mystic shotting a brush is a gamble that is (not by much but still) in favor of the person who played the brush. I also really want to know if the ambush is revealed when you kill the brush, if it isn't that's even more annoying. But it totally still is a "what's in the brush" mind game.
