I was looking one of my domain status at dnsreport.com and get following warning on root.
WARNING. The root servers (D.GTLD.biz.) are not providing glue for all your nameservers. This means that they are supplying the NS records (host.example.com), but not supplying the A records (127.0.0.1), which can cause slightly slower connections, and may cause some incompatibilities with some programs. This behavior is allowed by the RFCs. This will usually occur if your DNS servers are not in the same TLD as your domain (for example, a DNS server of "ns1.example.co.uk" for the domain "example.com"). In this case, you can speed up the connections slightly by having NS records that are in the same TLD as your domain
I think it's obvious how to avoid the warning. Have your domain's authoritative nameservers in the same top level domain as your domain.
Whether the warning has any weight, I don't know off the top of my head, and could never tell for sure without knowing the domain.
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