Potential DNS leak with openVPN on Linux

I have setup my own OpenVPN server. I push all traffic through the VPN with redirect-gateway def1 bypass-dhcp. For test purposes I use the Google DNS 8.8.8.8. I double-checked that /etc/resolv.conf just contains this DNS, ip route show seems to give correct results, traceroute shows the traffic is routed via my OpenVPN server. So I thought I am setup for success until I checked for DNS leaks (using ipleak.net with Firefox). This website shows me many Google IPs that my DNS is distributed to for load-balancing (see this answer), which is normal, but all of them are in the wrong country, near my current real location and not near my OpenVPN server.

So my question is: How does Google know and why do I get those servers? If I traceroute those, I can see the connection is routed via my OpenVPN.

edit: With Chromium, freshly installed, this did not occur at first, just local IPs around my server, but with a second try, it was the same result.