Has anyone verified that this actually works? My company's DNS administrators have already made this change. use-application-dns.net returns SERVFAIL when I run

Has anyone verified that this actually works? My company's DNS administrators have already made this change. use-application-dns.net returns SERVFAIL when I run "dig" on my machine on the corporate network. But if I enable DNS over HTTPS in Firefox, it very clearly still uses the Cloudflare resolvers. We have some split-horizon zones set up (resolve to 10.x IP's internally, and public IP's externally). When I tick the DoH box, Firefox starts resolving the public IP, verified in the Dev Tools network pane. Curious if the issue lies with us or Mozilla.