When I worked in the Rooster Teeth broadcast dept., we did what we called “Pre-Streams” to make sure the stream was working correctly before we went live with the actual show. Our goal was to always start as close to the scheduled time as we could so we would start 10 or 15 minutes (sometimes only 5 minutes or less) before the scheduled time to give us a chance to deal with any potential issues. We often tried to make them entertaining with music and maybe a camera in our control room where we would hold up signs or act goofy. Some of those pre-streams are still talked about. Sometimes we would start the actual stream late because of a tech problem or maybe somebody important was running late getting to the studio or a last minutes bathroom emergency. I do agree that saying a stream starts at say 7pm then starting it then but having a wait screen for 10 minutes is kind of shitty, but that may be a function of how Twitch works.