DNS lookups for CDNs will return a different (local) IP for clients in different regions. The proper way to handle this is using EDNS Client Subnet, which is what Google DOH does. CloudFlare DOH doesn't support this, but instead handles this by making the DNS request from a server near to the end user. This is only roughly accurate, and can't for example point a user's request to their ISP's on-prem edge cache: https://samknows.com/blog/dns-over-https-performance