I'm pretty sure Cloudflare is an ISP according to German law ("Diensteanbieter" according to DDG). You might confuse "ISP" with the terminology of "Access Provider" according to the (now defunct) ยง8 TMG.
If that were true, sci-hub.se would be blocked in Germany on 1.1.1.1 (1dot1dot1dot1.cloudflare-dns.com), it isn't blocked, therefore it's not true. (Modus tollens)
I am a Service Provider ("Diensteanbieter") according to DDG and I don't block a single page, which makes your statement not only wrong, but rather so wrong that not even the complete opposite would make any sense.