We had received clarification on the Nameserver IPs feature, and the nameserverips.yaml file from our developers. I wanted to share this to clarify the intended behavior.
The functionality of the "Nameserver IPs" page was changed in 11.30. It is now a report, and not a page meant to configure any aspect of DNS. It reports the nameservers used by zones on the server, as well as a count of the the number of zones that use a given nameserver.
The nameserverips.yaml file is automatically updated, and not meant to be altered by hand. It is a cache file, rather than a configuration file. Neither should the /etc/nameserverips file be altered manually. The script /usr/local/cpanel/scripts/updatenameserverips populates the yaml file automatically. This script retrieves the information it populates the yaml file with by scanning the zones on the server for NS records, then using /usr/local/cpanel/scripts/quickdnslookup to get the IP.
The correct way of updating the information on Nameserver IPs is through the "Basic cPanel & WHM Setup" page, and to ensure a proper DNS configuration. If the Nameserver IPs page is presenting incorrect information when DNS is set up correctly, this is a bug and should be reported via a support ticket.