I think it's a gimmick that Samsung will cut out in future models for cost savings reasons. Like Samsung ditched the edge displays, or the Bluetooth in their S-Pen, or like Apple ditched 3D touch.
You could try doing this[0] to your iphone... ([1]).
[0]: https://www.instructables.com/Privacy-monitor-made-from-an-o...
[1]: https://www.ifixit.com/Answers/View/570453/How+to+remove+iPh...
Reading comments here looks like most of the commenters didn't read past the title.
This is not the same as a privacy screen protector. The screen hardware itself can dynamically protect parts of the screen on demand down to pixel level, the OS can then dim only the app or notifications you want dimmed. There is no screen degrading for parts that are not in privacy mode.