There are two types of zombies:
Barrier zombies need barriers to move through first before it can do something.
Risers however automatically go after the players without using the barrier.
Long story short, you need risers for windowless barriers.
The issue has been fixed!
I didn't know the barrier spawners needed the whole barrier to make it into the map. In hindsight that makes a lot more sense now.
Thanks for the help, I won't forget this info.
Regular zombie spawners dont actually need barriers. Theres info about making the spawners "windowless" here https://www.ugx-mods.com/forum/help-desk/10/zombies-and-traverse/9021/msg99027#msg99027 You also need the kvp's script_string zombie_chaser. I've done this method before and it works