I might merge ISIS and al-qaeda together in this, but from the top of my head I remember them taking credit for the Norwegian mass murder that ended up being Breivik and claiming to have shot down a Sharm-el-Sheik - Petersburg plane (even posting fake video) with a missile that ended up being a bomb.
They don’t see these things as atrocities. For them claiming they did it even when it comes out as a lie is just publicity and moral boost.
ISIS doesn’t need to make up or take credit for anything. They create enough atrocities, yes atrocities, all by themselves. Doesn’t make any sense that you would want to blame this on the Kurds, why Kurds. Perhaps AQ, perhaps another Terrorist faction. AQ pretty much bowed to ISIS a while back. AQ’s fight for dominance pretty much disolved after Benghazi.