How to access webform field labels in a twig template?
Your last comment:


  Well that isn't very intuitive. It would be nice to just access
  everything directly in the twig template.


OK, then try different templates:

When the form theme wrapper is executed the inside of the wrapper is already rendered in {{ children }}. Don't try to render the form again, use this template only for the form tag and the outside container:

webform--contact.html.twig

&lt;div class="container"&gt;
   &lt;form{{ attributes }}&gt;
   {{ title_prefix }}
   {{ children }}
   {{ title_suffix }}
   &lt;/form&gt;
&lt;/div&gt;


Use for the inside of the form the #theme template itself:

webform-submission-form--contact.html.twig

    &lt;div class="row"&gt;
        &lt;div class="col-md-6"&gt;
        {{ form.name }}
        {{ form.email }}
        {{ form.subject }}
        &lt;/div&gt;
        &lt;div class="col-md-6"&gt;
        {{ form|without('name', 'email', 'subject') }}
        &lt;/div&gt;
    &lt;/div&gt;


Finally you can theme the form element in form-element--webform-email.html.twig