I followed these steps in a local environment:

• Created the test program.

• Created the course set.

• Assigned the audiences.

The emails were sent to all users equally. Those who were part of the audience and had previously completed the added course received two emails: one for the assignment and another confirming their prior completion.

Ideally, users who have already completed the course should not receive any emails. It seems like they are being reassigned, but then the system recognizes their prior completion and sends the second email.