I can understand your skepticism, but there is more to performance than just running a single pagespeed test. I know you've already included time to first byte, but also consider:
- Time to first byte
- Time to first render
- Critical render path
- Fewer HTTP requests
- CDNs close to the user (@bep already mentioned this)
- All the other build tools the frontend world uses for things like concatenation, minification, image optimization, etc.
The docs concept site--obviously built in Hugo and also hosted on Netlify--is rocking a 100/100 (and will soon be much prettier thanks to @budparr.
So even if a single test shows a marginal difference for you as a single user, there are a lot more considerations, not the least of which is actual vs experiential performance. Also, I don't think the question was whether "Can Wordpress do this?" as much as it was "Can Wordpress do this as effectively as Hugo and a JAMStack solution as developed and supported by Netlify?" The video also talks about consolidating the different platforms, using Netlify's really slick and intuitive SPA CMS layer, and the beauty of outsourcing all your backend worries to a company that just kind of "takes care of all of it." There are tons of improvements to authors and editors for the site too...all thanks to Hugo:)
That said, I can see why Netlify would focus on speed because it's an intuitive and quantitative metric, but there are so many other reasons to use Hugo over Wordpress that maybe their PR just didn't prioritize. (I trust their decisions.) For one thing, content is considerably less exportable in a WP install. Wordpress requires a relational database and has, in many ways, a much stricter content data model than Hugo. You can write in markdown in Wordpress as well, but that's an indication that the tool itself can't ignore the brilliantly simplistic model of small, well-composed, self-contained content files with embedded metadata.
As an example from my job, I took a couple thousand notes (Markdown files), generated them into a responsive website with search (using lunr.js) for my colleagues on an internal-only site, and then used pandoc to spit them out into PDFs and other formats. This setup took less than a day, and now all the content (which my job requires me to give top priority) isn't dependent on any of the aforementioned tools. The site builds in less than a couple seconds too, which is freakin' incredible.
Wordpress can offer much of the above but not without adding complexity at an order of magnitude...
I can expand if you need more examples.