POE2: Occult Spell Cast Locations

I've been playing using WASD to move:

I've noticed that when casting Contagion it will often cast on a monster that is further out than the monsters I specifically clicked on to cast that are closer. Additionally, when casting Essence Drain, it doesn't cast where my mouse cursor is located, it will cast screen-wise above where the cursor is located. Sometimes it won't even cast in the direction of my mouse cursor. I was fighting Zalmarath and I could be targeting any spot on his colossal body with my cursor, but the spell would be cast at his left hand. As a result, I had many missed casts, despite that my cursor was over his body.

I find it strange that there seems to be some kind of auto-targeting aspect instead of just being cast where the mouse cursor is located on the screen.