What's the diff between instant messaging properties in Contacts dictionary?

In Catalina at least, the ‘instant message’ class in the dictionary of the Contacts application has properties called ‘service name’ and ‘service type’. The latter is an enumeration of services such as AIM, Facebook, Jabber, Skype, etc. The former takes a text value (or missing value); the actual values in my own Contacts database are all “Facebook”, “Skype”, or “twitter” (sic). Does anyone happen to know why these exist as two separate properties and how they’re meant to be used? In the UI of the Contacts app itself there’s a pop-up with options corresponding to ‘service type’ enumeration along with a label popup and a text field for the username, but as far as I can see there’s nothing corresponding to the ‘service name’.

Just guessing after looking at the dictionary and Xcode’s documentation for the Contacts framework, might the string be the localized name for the service?