Pi-Holes hostnames sometimes UnKnown when using dig or nslookup

[mx2k]

I tested DNS availability a bit with my Pi-Hole, using all assigned IPs. I run it with unbound as upstream DNS on localhost. There's something about the server hostname now showing at 1.

I can see Server: UnKnown at 1.
I can see defined server names at 2. and 3.

The hostnames are defined as follows:

1. fe80:: local IPv6 address + hostname rpi-dnshole.fritz.box in /etc/hosts. Server hostname is reported incorrectly.
2. 10.1.1.6 IPv4 address + hostname rpi-dnshole.fritz.box in /etc/hosts. Server hostname is reported correctly.
3. 2a00:: IPv6 and hostname rpi-dnshole defined in some config file by running pi-hole -r. Server hostname is reported correctly.

Should it show UnKnown at 1.? If not, how can I make it report the hostname for the link lokal IPv6, as it does with the other assigned IPs?