Drupal 8 Custom Composite Masked Input Are masked inputs supported in custom composites?

I've tried the following and it doesn't break but it also doesn't mask.

$elements['job_details']['job_phone'] = [
  '#type' =&gt; 'textfield',
  '#input_mask' =&gt; '(999) 999-9999',
  '#title' =&gt; t('Company Phone Number')
];
If you want to get simple form elements to include webform element enhancements you have to 'initialize' the composite's sub-elements using \Drupal\webform\Element\WebformCompositeBase::initializeCompositeElements