It seems this was caused by something in the Alpine setup process inside the KVM guest. It didn't occur when running the basic setup-alpine but did occur when doing a manual setup (e.g. custom disk partitioning).
There is no connection between host OS and guest OS regarding this.
It is Alpine Linux that assigns the permissions to the device node. They have had bugs related to this earlier: https://wiki.alpinelinux.org/wiki/Release_Notes_for_Alpine_220.127.116.11
You need to check with Alpine Linux developers why the permissions are setup like that. Most likely it is ...