Custom composite label on mobile view indent issue

I am not able to replicate this issue using the below example and the Claro theme. What theme are you using?

webform_custom_composite_basic:
  '#type': custom_composite
  '#title': webform_custom_composite_basic
  '#multiple__header': false
  '#element':
    first_name:
      '#type': textfield
      '#title': 'First name'
    last_name:
      '#type': textfield
      '#title': 'Last name'