Why do theme functions only run once?

I am trying to set a default value in a form using static Theme function. However it seems theme functions only execute once, a page refresh does not update the page values.

Have you disabled the (twig) cache for this page?

Yes I have set cache_enable: false. Here's the folder structure for your reference -

- 01.home
  - default.md
- 02.demo
  - form.md

Frontmatter for form.md (under 02.demo folder) is as follows -

---
title: Demo
cache_enable: false
form:
  fields:
    - name: name
      type: text
      label: Hello World
      data-default@: ['\Grav\Theme\Antimatter::getQuery', 'product']
---

Seems like this problem has been around for some time.
/forum/forms-blueprints/form-field-set-by-url-parameter-t9281?u=gnat