A Referential Member of a collection is a resource. (Req 3.1.15)
It can have properties (Req 3.1.9), and always has certain DAV properties. Most importantly, the value of DAV:reftarget is the URI of its target resource, satisfying Req 3.1.6 that it is possible to obtain the URI of the target resource of any referential resource.
The DAV:resourcetype property of a referential member always has the value refmember. Satisfies Req 3.1.12 that it be possible to discover whether a collection member is internal or referential.