We do not use the CW GUI to rename computers. We use a process that is typical for an AD centric IT department. As part of the deployment/preparation for an end user, the built in processes for renaming a Windows workstation are used. This is to ensure that AD/AzureAD are satisfied with proper renaming processes. Since AD is our focus and must absolutely be correct, we would not employ any external method for renaming. Using this method, CW is not satisfied and does not reuse existing sessions. 

How are you doing renames? We see dupes after we rename systems. The old name persists as a separate session. 

As Alex said above, 2 years ago, there are several unique items about every computer that could be used to ascertain that it is in fact the same system. Reconnecting a machine that was reimaged (or just renamed) to an existing session is the preferable method. 

This happens when a computer is renamed also. We image computers and give them a "STOCKxxxx" name where the X's are the asset tag number. Then, when we rename the device to deploy it for an end user, the old STOCK name still persists. Using something like the serial number and/or GUID is all that is needed. If the machine was just renamed, simply rename the old session. There's no need to create a new one at all. The same goes for a reimage. There's enough unique info about any one machine that multiple checks could be used.