That's just the functionality of ground placed AoEs, whether they follow the player or not. These effects actually create a sphere of their influence, which is projected onto the ground as a red circle. Negate is the most obvious example of this, and caltrops probably the most common, due to its size. In both cases, you get hit through any and all line of sight, be it roof, wall, or floor, so long as the character's feet (not necessarily head, for example) are in it. I think it is because these AoEs functionally do not have line of sight that infernal guardian initially did what it did.
I got killed on the second floor tower on the bridge from a destro ult in the first floor tunnel going to the bridge ramp. Typical...