--------------------------------------------------
2.1. Registries offering searchable Whois service (e.g., per exhibit A of their RA) MUST support RDAP search requests for domains and entities. Entities MUST be searchable by name search pattern as defined in RFC7482 section 3.2.3 in order to allow for searches by contact name or address. Boolean search capabilities (AND, OR) MUST be supported, when a RFC defining this capability has been published.
Domain and entity searches are specifically mentioned, but nameserver searches are not. Does that mean that registries need not support nameserver search? Or was that an oversight?