The mDNS sections in part 12 do nto describe what is required well enough for someone to implement the "Discovery Server Announcement using mDNS" conformance unit
I would suggest that the 4.2.3 section have the following text updated:
"Dedicated systems (usually embedded systems) with exactly one Server installed may not have a separate LDS. Such Servers shall become their own LDS or LDS-ME by implementing FindServers and GetEndpoints Services at the well-known address for an LDS. They should also announce themselves on the MulticastSubnet with a basic MulticastExtension. This requires a small subset of an mDNS Responder (see mDNS and Annex C) that announces the Server and responds to mDNS probes. The Server may not provide the caching and address resolution implemented by a full mDNS Responder. "

to say
"Dedicated systems (usually embedded systems) with exactly one Server installed may not have a separate LDS. Such Servers shall become their own LDS or LDS-ME by implementing FindServers and GetEndpoints Services at the well-known address for an LDS. If implementing an LDS-ME, they should also announce themselves on the MulticastSubnet with a basic MulticastExtension. This requires a small subset of an mDNS Responder (see '"Multicast DNS responder" 'in mDNS ) that announces the Server and responds to mDNS probes. In addition they shall implement additional OPC UA specific items described in Annex C. The Server may not provide the caching and address resolution implemented by a full mDNS Responder."

The CU lists
"Server announces itself on a MulticastSubnet with a MulticastExtension (subset of an mDNS Responder)."
which is acceptable if the part 12 text is updated
but the Facet description is :
"Support of this Facet enables discovery of the Server on a subnet using mDNS. Support of this Facet enables discovery of the Server on a subnet using mDNS. This functionality is only applicable when Servers do not register with an LDS."
(Facet only has the one CU - the second half of the facet description
'This functionality is only applicable when Servers do not register with an LDS." does not make sense and does not appear anywhere in the text (also implies a requirement, but is not tied to a CU (so not tested))

Either additional CU or addition text for the existing CU is needed or the second sentence should be deleted. If there is a restriction on what device can implement an mDNS responder - then Part 12 should also be updated with additional text in either annex C or in section 4.2.3