alt Hacker NewsCompletely different thing. A littlesnitch type thing is for all traffic. Pihole is a DNS query thing that prevents various ad content from being loaded. It's also trivially easy for a malicious application with network access to bypass any instance of pihole on your LAN by doing its own DNS over HTTPS lookups to its own set of server(s) by IP.
I mean, if you're at the point where your machine is compromised by a process with full network access little snitch won't help much either.