I imagine the fact that they allow the embedding of videos on other sites make it hard to restrict the playback to that degree. There seems to be a tipping point at which they’ll work on breaking something, more than likely based on it’s popularity When enough 3rd party frontends figured out background playback, they took the time to develop a way to break it. I think the same will happen when they feel too many people are circumventing their data scraping, ads or algorithms. They’ll finally go all in but it’s clear that they don’t want to do that just yet.