The concept of assumed-connection will change. Currently we mark
connections that are generated and assumed as "nm-generated-assumed".
That has several consequences, one of them being that such a settings
connection gets deleted when the device disconnects.

That is, such a settings connection lingers around as long as it's active,
but once it deactivates it gets automatically deleted. As such, it's
a more volatile concept of an in-memory connection.

The concept of such automatically cleaned up connections is useful beyond
generated-assumed. See the related bug rh#1401515.