In HSDS, multiple Contacts can be associated with a service or organization, each with their own Location and Phone details. Within this IG, a Service can have multiple locations and phone details but you can not specify the contact to which they relate too.  Meanwhile, Organization here does have contact information, however does not have the full Location information, like Contact does in HSDS.

Adding a contact section to the Service would improve alignment. We wouldn't say this is a critical issue that absolutely needs to be addressed in this release, but it is one of the most significant limitations in alignment between the two data models.