It’s because of this:

$ dig +short insights.navidrome.org
209.141.42.198
$ dig -x 209.141.42.198

; <<>> DiG 9.20.11-4-Debian <<>> -x 209.141.42.198
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 12665
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;198.42.141.209.in-addr.arpa.   IN      PTR

;; ANSWER SECTION:
198.42.141.209.in-addr.arpa. 30 IN      PTR     demo.navidrome.org.

;; Query time: 208 msec
;; SERVER: 192.168.1.1#53(192.168.1.1) (UDP)
;; WHEN: Sun Mar 08 17:13:34 CET 2026
;; MSG SIZE  rcvd: 77

In practice, demo and insights are on the same IP, whose reverse points to demo