Gateway DNS use a distant server

Hi, I have been using Gateway DNS from Zero Trust and I have noticed the following:

dig +short CHAOS TXT id.server @1.1.1.1
“ATH”
dig +short CHAOS TXT id.server @172.64.36.1
“LHR”

I live in Athens, so “ATH” is my local datacenter, but instead of that, Gateway DNS connect to “LHR” (Netherland). Also dnsleak.com shows that i use a server from the UK.

Any idea what could be wrong?