Seems like it's exploiting a hole in YT's reporting process. I stumbled on a few of these streams last week and tried to report the accounts for "impersonating". However, on the reporting page, you're asked to specify which of the users' videos or comments are violating the rules, but you're not given any option to specify a live stream video. Since the accounts did not post any other videos or comments, there was no content for me to tag.

I submitted the reports anyway and, shortly thereafter, got an email from Youtube telling me "Unfortunately the information you provided in your report to YouTube does not meet our impersonation reporting guidelines." Seems they automatically ignore any reports without tagged videos/comments.