Been testing it in sandbox. If your CTRL+K your Ythota, and does small initial damage to your units, but then 0 damage if there are no enemy units within its range, if there are some enemy units, it damages them and your units until there are no enemy units, if you spawn it with ALT+F2, it damages everything.
Did something change? I remember it always damaging everything around.
You can also see it here: https://youtu.be/O1S-30JVppE?t=2609