Filter by request-only sub-categories?

From the End User Portal > View Your Service History, end users are able to see a list of all the service records (Incidents, Requests, etc) they have submitted. When clicking on "Sub-Category" to set a filter, not all available sub-categories are listed. Sub-categories that are only available as a request are missing. Is there a way to add request subcategories to this area?

Under Service Desk > Categories, the categories are enabled in the EUP, and are visible to all users groups and admins.

Any help is much appreciated. Thank you!