ms-teams deleted account question

Hi all,

My question is this: a colleague working in a MS-Teams chat noticed two notifications of users that  supposedly left the chat. As in: by their own doing. 
One thing that strikes me odd is that those two useraccounts were disabled and deleted way before. One of them even more than a month. 
I can only image that a teams-manager has been clearing up chat members. But then again I would expect a different type of notification, like: UserX has been removed from the chat.

Any clues?