Thanks to some sleuthing by Dana, David E. and Nga, a mystery has been unraveled. According to SCP:
“To request the cataloging of a single open access title not part of any specific collection send the request via the CDL Help Desk (helpline@cdlib.org). Provide the URL for the resource and a statement requesting SCP cataloging. Note, these “unreviewed” cataloging requests are of lowest cataloging priority and will be done as resources are available.”