facets-item-list.html.twig overrides attributes, and they replaced by JS for certain widgets

The facets-item-list.html.twig template documents the attributes variable, but overwrites it:

 * - attributes: HTML attributes to be applied to the list.

SNIP

{% if context.list_style %}
  {%- set attributes = attributes.addClass('item-list__' ~ context.list_style).addClass('cake') %}
{% endif %}

SNIP

  {%- if items -%}
    <{{ list_type }}{{ attributes }}>

Furthermore, if using, say, the dropdown widget, then the list HTML element will get replaced, and AFAIK any attributes there won't be in the resulting HTML output.