No. Items you have turned on in the knowledge base in Collection Manager that do not have OCLC numbers will still surface in WorldCat Discovery. An OCLC number is required to output a MARC record and to set holdings in WorldCat. If an item does not have a holding in WorldCat and is not treated as held, this will influence how and where a title surfaces in search results in WorldCat Discovery.
Links will surface but because holdings in WorldCat are not set, items might not be marked as held by your library. However, knowledge base titles with associated article citations in the central index will show as held by your library based upon ISSNs; Your library can opt to use full text coverage from the knowledge base to determine whether or not an article is held by your library.
When you perform a search, altering the scoping level (Libraries Worldwide, Your Library) and sort options (Best Match, Recency, Library, Most Widely Held, and so forth) can change how high up an item surfaces in Discovery search results because these options factor in held status.