Discrepancies between Territory2 and Group DeveloperName

Why am I seeing discrepancies between Territory2 developer names and Group developer names? 

Internally we generate the user group developer name from the Territory2 developer name. However, if the group developer name has a collision with another group developer name, then it will start appending numbers to the end of the name.
 

There could be numerous reasons why this might happen but the most common reason we see is if the organization had Territory Management 1 enabled in the past, then disable it (TM1 does not delete user groups for the TM1 territories). When a customer migrates to TM2, if they use the same names for some of the territories, then the group names would collide. Thus it is generated.