Here's their "10 popular sites using Wordpress"
- microsoft.com - It's not wordpress, probably home grown
- wordpress.org - This one's a freebie
- digicert.com - Using Adobe Experience Manager, per script includes
- wordpress.com - Another freebie
- mozilla.org - No, using a homegrown CMS: https://github.com/mozilla/nucleus
- nih.gov - It's using Drupal, per a meta generator tag
- forbes.com - No real for or against evidence, though the lack of any wp- paths leans a little more against it being wordpress
- archive.org - It's some type of react app, not wordpress. Probably home grown
- nginx.org - Just... no.
- ebay.com - Would it surprise you, no.
I have serious questions about their methodology.
Similarly, just because sites like Techcrunch use Wordpress, doesn't mean they're doing it by having someone upload files over FTP to some cPanel managed Godaddy account.