"At CloudFlare TTFB is not a significant metric." People might think that this article is written to educate masses. The thing is - if you take webpagetest.org and run speed tests with and without Cloudflare, in MANY cases 'Load time' will actually be slower WITH CloudFlare. And the biggest difference will be in TTFB.

Why does it happen? Cloudflare works as a proxy, taking HTML from your server and returning it to a user in optimized form. Because all requests go through their servers - there's one additional hop. With this hop TTFB increases significantly.

Although I agree that TTFB is actually not that important from end user's perspective, the reason why Cloudflare wrote this article is strictly marketing.