Per the Polaris support team as of September 2023, SIP2 only supports communication about holds where the associated item is in "Held" status. Holds requests in other statuses are 'invisible' to third-party services communicating with Polaris through SIP. When I brought this up, our site manager recommended putting in an enhancement request. Apparently there were some older ones on IdeaLab that have not been carried over to Idea Exchange.

I was skeptical that there would be anything Clarivate could do from within an ILS to make this change since it sounded like a SIP limitation rather than an ILS limitation, but while researching the issue I came across documentation for Alma, which is also a Clarivate-owned ILS, suggesting that that ILS IS capable of passing information about holds in statuses like Active and Pending via SIP: https://developers.exlibrisgroup.com/alma/integrations/selfcheck/sip2/ (see the listing for "holdItemsCount")

It would be great for this to be replicated in Polaris. Right now, a patron accessing account information via a third-party service like a self-check machine or an automated phone system is given inaccurate information--a patron with one hold in Held status and one hold in Active status would be told they have "one hold" which is factually incorrect.