Pre assigned breakout rooms not working

I am testing the pre-assigned breakout rooms ahead of a meeting. I uploaded the csv file with room names and email addresses. After starting the meeting to test that it works, I found that users who joined were reflected as unassigned. There doesn’t seem to be a way to capture their email ID upon joining as they could just enter the meeting ID. Even when they renamed themselves to their email ID, they remained unassigned.

What is required for participants to be recognized as assigned upon joining?

I just had this exact same issue - is there a fix?