You mean the mirror image thing?
The basic idea is, they can delete videos, but folks can repost deleted videos, either verbatim (or whatever the term is for video) or with alterations, such as mirror imaging. That makes it hard to censor videos and still have a YouTube. Anything that makes it hard to censor videos is A Good Thing!
Of course, the downside is, something happens, gets videoed one or more times, gets uploaded first instance, second instance, first instance mirror image, second instance with narration interspersed, etc. IOW, one incident can be videoed multiple times, each of which can be uploaded with multiple alterations, malicious or not. That can make it hard to isolate the primary source videos, while making it hard to censor.
Yes, the ‘mirror image thing’ that people keep saying are different videos from different angles. It’s hilarious.