Fun with DNS resolutions fail on hyphenated domains

When asking one of the Fun with DNS type resolver (e.g. email or SMS), the system fails to answer when using just an hyphenated domain name:

Cloudflare-dns.com

Sorry but queries for Cloudflare are not supported. Please try again using a different query type (such as A, AAAA)

If forcing the query type, it does work:

A Cloudflare-dns.com

43.243.131.114

1.1.1.1 is a partnership between Cloudflare and APNIC.