Golems appear to cast Frozen Spear, which is created on his tile, then takes a step towards the enemy, thus moving infront of the Frozen Spear projectile.
Then the spear gets its turn and moves forward, hitting the golem.
Here is a picture where you can see the golem infront of the spear projectile. On the next turn he gets hit by it.
I don't know if this has been addressed yet, but I'm pretty sure this happens because all the attack runes are instantaneous cast now. This affects all actors. Hence, to reproduce, simply infuse an attack rune to a character, fire the rune, then move in the direction that you fired.
Yeah, NPCs with frozen spear runes hit themselves all the time. I think it's really the only one affected, since all of the others have no travel time.
Sorry about all the parentheses (sometimes I like to clarify things).