They don't talk much about the challenges. It is a ton of work even on the backend to get the amount of SLI coverage and in the shape needed to effectively calc

They don't talk much about the challenges. It is a ton of work even on the backend to get the amount of SLI coverage and in the shape needed to effectively calculate an error budget. Even then you can introduce changes that might break functionality in stealth ways.. Doubly so for the front end.