For Courses and Programs, once you are enrolled, you are enrolled and you cannot be enrolled again unless there is an expiration.
This is not true for Live Training. If three different Smart Groups are enrolling you in a Live Training, you will have to complete the Live Training three different times. This means that just for Live Trainings, we have to keep track of where the different enrollment sources are coming from and try to eliminate the chance of any duplicate enrollments.
I cannot see the use case for this and it seems like it is just a hold-over that hasn't been updated.