It's for futureproofing. The console should be able to output 8K for:
- 8K physical media
- 8K streaming
- Upscaling 4K games on 8K TVs
- Checkerboard rendering (or similar techniques) on 8K TVs
The PS4 Pro outputs at 4K yet renders at like 1800p
This is absolutely correct. There is no further need for discussion on this subject. The PS5 is 8k capable, it has nothing to do with gaming necessarily. It is a positive thing though, by the end of the consoles life cycle 8k video formats will most likely be much more prevalent.