Cannot disable anchors in a specific page.

I cannot disable anchorjs in my custom error 404 page.

You can find the exact page setup I'm using here: https://github.com/RojerGS/mathspp/tree/master/pages/error. And you can test it by accessing a random route in my website, e.g. https://mathspp.com/agadfasdfasdfaff.

My frontmatter.yaml looks like this:

anchors:
    active: false
    enabled: false
http_response_code: 404
metadata:
    author: Rodrigo Girão Serrão
routable: false

and my default.en.md looks like this:

---
title: Error
---
<center><h1>Error 2×2×101</h1>

Woops. Looks like this page doesn't exist.
</center>

But for some reason, the anchor to the h1 title is there.

getgrav / grav-plugin-anchors