Rumors pointing to custom locations spitting out unexpected data

[ArmandVestibule]

Consider this scenario:

Fabric 1.20.1, latest MCA available at time of writing.

I have added an array of custom structures to the rumors list in the mod config, as per https://github.com/Luke100000/minecraft-comes-alive/wiki/Custom-Rumors-and-Destiny-Structures.

I have also created a datapack and placed an updated en_us.json file in the path: PACK>Assets>NAMESPACE>lang

Pack has been applied (there are custom recipes in there that are showing up in NEI) and server has been rebooted, yet I get some bonkers output.

Samples:

Config:
  "structuresInRumors": [
"minecraft:ancient_city",
    "minecells:overworld_portal"
  ],

en_us.json:

"dialogue.location.overworld_portal/1": "Rumors circulate about an overworld portal hidden within %2$s, a gateway to otherworldly realms.",

Ask for rumors from a villager. Output:
[System] [CHAT] Annabelle: #Gmale.#EFRAGILE.#Pleatherworker.#TADULT.dialogue.location.overworld_portal

I am clearly doing something wrong, and I have a feeling it's fundamental. Any advice?