interesting my take on that is :
"In the Black Mirror universe, Netflix is a major streaming service, but it is also seen as being somewhat generic and uninspired. Streamberry, on the other hand, is a newer streaming service that is seen as being more edgy and original.
By having Stuart mention that Netflix documentary, Waltonville Claw it sounds like the writers taking a dig at the fact that Netflix is often seen as being a home for bland and forgettable true crime documentaries and might be suggesting that Streamberry is a better place for more original and creative content.
Not to miss the fact that Davis's documentary eventually streams on Streamberry is also significant. Also a potential hint that Streamberry is a more successful streaming service than Netflix, and that produces quality content "