The article linked and referenced above (describing this as baked into the ecosystem of the future) is about the Young Vic. The Old Vic, which streamed Lungs, Christmas Carol etc., had FAR more streams available than 500.
I think you’re right that not every single performance of every single show sold out. But I believe the statistic was that the first three performances back last summer sold over 300,000 tickets to people in more than 70 countries. That’s not insignificant. (And certainly doesn’t make it a good comparison for Titanique, which I’d never heard of until your post the other day.)