No he is saying that whitehouse.gov uses WordPress CMS, not wordpress.com. It's open source software, tons of sites use it, like 35% of the top million websites or something like that. I use it on some of my projects. Hussein's whitehouse.gov used Drupal if I remember correctly. I use Drupal sometimes too.
See this URL: https:// www.whitehouse.gov/wp-content/uploads/2017/12/wh.gov-share-img_03.png
That's how WordPress stores files uploaded to a site, under a wp-content directory/folder.