> You would record a video offline and then upload it to Youtube
I can't speak to how popular this feature actually is, but the YouTube app includes video recording, so not everyone is going have a local copy of their work, by default. Conversely, who uses the Medium editor, rather than, say, Google Docs?
One big difference with Youtube is you don't create your work on their platform directly. You would record a video offline and then upload it to Youtube so you have a copy of your work by default.
With Medium, chances are you wrote the article directly on their platform so now if it gets removed from their site you probably don't have a local copy of it so it's gone forever unless it got scraped somewhere.
In either case I think Medium is really bad and I wouldn't use it.