A new APK teardown by XDA Developers of Netflix v7.58.0 shows code snippets with the label “partial download” and phrases like “You need to download a bit more to start watching” and “You've reached the end of what's been downloaded so far. Please connect to the internet to continue watching”.
This could help if you want to watch twenty minutes of an hour’s show on the bus but don’t have any data left and only have two minutes before you have to leave. The whole episode might not download in time, but if the first twenty minutes has then you’ll be covered.
Other user benefits could be to save data or to download something partially to avoid buffering if your connection is dropping in and out. But that’s getting into the weeds a bit here – partial downloading will be great if it means getting round the frustration of sitting down on a plane or train to watch something and seeing there’s 1MB left to download and not being able to.