There is a long-standing dispute between Cloudflare and Germany's biggest ISP, Telekom, which results in terrible peering for Cloudflare free traffic for Telekom customers here. Sites on the Cloudflare Pro plan are not affected by this somehow.
If the author is a Telekom customer, then they would absolutely see 100ms+ improvements.
DTAG is just terrible. Having a whitelist of allowed mail providers they deal with? Check. Abusing peering to squeeze more cash? Check. Advocating for censorship on the Internet? Check.
>Sites on the Cloudflare Pro plan are not affected by this somehow.
This has been my general experience with cloudflare. Their free plan is abysmally slow. And even their Pro plans add significant (30ms+) overhead to requests.
If the author is a Telekom customer, then they would absolutely see 100ms+ improvements.