Leader of the Pack Achievement when making first potion

Got the fabled leader of the pack achievement, after brewing an awkward potion, in normal survival/vanilla minecraft. I'm in peaceful mode, if that helps. I've been looking for wolves for days, but I haven't tamed any. I was expecting a potion-related achievement, but this one popped instead. Could be a possible exploit. Here you go, Mojang!
Also, about five minutes prior, while in peaceful mode, I could hear a Ghast meowing but I could not see it.