Isn't this because Netflix (fast.com) has better peering agreements with most ISPs while Cloudflare relies more on their own infrastructure?
More likely, Netflix has better infrastructure and better peering agreements, than Cloudflare. Which is kind of surprising, since Netflix is supposedly a media company and Cloudflare is a "internet" company.
[1]: https://netflixtechblog.com/building-fast-com-4857fe0f8adb
[2]: https://openconnect.netflix.com/en/#what-is-open-connect
I think there's something about the methodology of Cloudflare's test.
A thought, though: Cloudflare reports your p90 time as "your speed". I don't know what the other sites report. Is it the same?