People make a lot of guesses as to why the AI does something and it is often wrong. I see people test their designs with a bunch of the same zombie thinking the other types will do the same thing, which is sometimes not true.
Blood moon spawner does attack your base from multiple directions, but not all at once, it changes over time, because that is more efficient for pathing. The typical dumb zombie will not go very far to find a weak spot or opening, often preferring to beat on a wall near it instead of walking a bit to go through an opening. Yesterday I was just looking at that issue of being too dumb and beating the walls around a cemetery POI instead of using the opening, but really that is correct, since those are set to be that dumb. Thick walls would change that behavior, just like many things can change their behavior.
No zombie auto targets you except for blood moon spawns and POI volumes set to attack.