HR Case represents the sn_hr_core_case table which is the parent for all of the COE tables. Another option could be to filter out the HR Services on that table using Limit Services option on the HR Administration > Case Creation Configuration config page. You will still see HR Case as a selectable option but you will not be able to create the case since no HR Services are selectable.

This is also a great enhancement request to make this more configurable. I suggest submitting an Enhancement Request through HI to capture this recommendation.