This is most likely a bug, it has already been reported. These sqms have an invisible barrier on each of them that works like a wall, in a way that you can throw spells through them. If you use something on target you'll see the message "You cannot throw there". I believe it's a simple map bug, this problem also appeared on the recent WU 2020 TS on a specific area that used to be unreachable (part of different seas) and was fixed.