The tailscale interface does not generate any "Interface Statistics". I have tested this by generating traffic over taiscale via LTE.
I figured it out.
working scenraio:
A records are definded in domain dns (HETZNER in my case). IPs coming from tailscale are detected as such.
not working scenario:
using OPNsense as global dns in tailscale. Remote ips are always the ip of caddy resp. OPNsense.