Invite Contacts as Guests feature - Updates Not Linked?

I think I addressed this point in https://www.petri.com/office-365-groups-mail-contacts. 

"Behind the scenes, Office 365 creates a new guest user object using the properties of the mail contact. The mail contact is unaltered so that it continues to appear in address lists and keeps its membership in distribution groups."...

"Two objects with the same email address now exist in the tenant. Over time, when guest user objects offer the same functionality as mail contacts, you might be able to remove the mail contacts."

The issue is that each object serves different purposes. Guest user objects don't appear in the GAL, DLs, etc. whereas mail contacts do... One object comes from Exchange, one is essentially adapted from SharePoint sharing.

I can see why Microsoft adopted this approach to solve the problem as a lot more engineering effort would probably have been needed to upgrade mail contact objects to act as external guest user objects.