This is more likely the actual incident report:
A change made to how Cloudflare’s Web Application Firewall parses requests caused Cloudflare’s network to be unavailable for several minutes this morning. This was not an attack; the change was deployed by our team to help mitigate the industry-wide vulnerability disclosed this week in React Server Components. We will share more information as we have it today.



30 is assuming you write code for all 30 days. In practice, it’s closer to 20, so 75 tests per day. It’s doable on some days for sure (if we include parameterized tests), but I don’t strictly write code everyday either.
Still, I agree with them that you generally want to write a lot of tests, but volume is less important than quality and thoroughness. The author using the volume alone as a meaningful metric is nonsense.