Additional meeting and call-related features and issues within Microsoft Teams for business
Hello Patrick,
Based on your description, I did a lot of more research on the Teams Direct Routing with Final Microsoft subcode, and as far as I know it is a kind of API based code which owned by Microsoft. For your reference https://docs.microsoft.com/en-us/graph/api/resources/callrecords-directroutinglogrow?view=graph-rest-beta.
However, I can only find limited public Official article related to the real means of these codes reflected from backend. And these codes are from the Microsoft Teams backend to represent different scenarios when you got different codes. For some other information I'd like to share with you in Private Message (PM), please check at your convenience, thanks.
Best Regards,
Oliver