I’ve attached a picture to better see how this bug works.
If you select a villager and then select to build a wall, you can see a shadow anywhere on the map where enemy walls are located. See in the screenshot how there is a shadow between the trees. This means theres an enemy wall there. Theres no distance limit to this. You can see enemy wall placements all the way across the map like this. Makes it super easy to see which side of the base to attack from without having to even scout.