Cloudflare doesn’t cache HTML pages by default only static files https://support.cloudflare.com/hc/en-us/articles/200172516. You need to specifically tell Cloudflare to cache HTML pages via page rules etc https://support.cloudflare.com/hc/en-us/articles/202775670

Cloudflare Workers don’t cache by default either for HTML pages only static files unless you write the Worker to cache HTML pages.

So if they tested on default index.html page then it would of been a Cloudflare Cache miss/bypass which may explain their results.