You're essentially resolving non-existent domains through their custom DNS server. For example: dig 100USD-INR.fx @dns.toys Translates into "resolve 100US

You're essentially resolving non-existent domains through their custom DNS server. For example: dig 100USD-INR.fx @dns.toys Translates into "resolve 100USD-INR.fx using dns.toys as a DNS server". They then return TXT records containing the actual answer. Since .fx is a non-existent domain, they're not impersonating anyone, and if you switch "@dns.toys" with say "@8.8.8.8", it wouldn't resolve to anything.