what if everyone agrees on a 10s delay?
For pseudo-live streams such as sports events, that would be totally fine. People can have slightly out of sync streams, delayed by various amounts.
But you can't live stream a conversation with someone if you have a 10s delay.
The issue is everyone is watching the same part of the file at the same time. Offsetting by 10 seconds does not change that.
The time offset impedes the ability of viewers to interact with the streamer via chat, which for many people (incl. myself) is the whole reason to watch live instead of a recording.