See #8841 for use case:
...
Sometimes a issue should be assigned to more than one person at the same time (for example change requests in our case are assigned to the project Change Control Board). It would be useful to have under the project settings a way to create groups of users and have its name available in the assign to dropdown list along with other users, so when a taks is assigned to the group an email notification is sent to all group members.
...
If and when #2964 is changed to allow issue assignment by Role rather than Group, you'll be able to create a Role for your Change Control Board members and assign issues to that Role.