fieldConfig and checkboxTemplate

It seems whatever I do, “checkboxTemplate” is not doing its thing.

View form file (twig):
{% set form = active_form_begin({ 'fieldConfig': {'checkboxTemplate': "<div class=\"SOME_OTHER_CLASS\">\n_something_something_\n</div>"} }) %}

And checkbox list:
{{ form.field(model, 'id').checkBoxList(model.getCheckboxList(), {'unselect': null}).label(null, {'class': 'form-label'})|raw }}

What I get is still the default checkboxTemplate found in the ActiveField class, meaning my checkboxes are still styled by ActiveField::checkboxTemplate.

Am I doing something wrong?