ios 를 공부하는 중입니다. PartialKeyPath에대해 알고 싶은데 이해하기가 쉽지 않네요.

아래링크가 Apple 에서 제공하는 documents맞나요? 너무 설명이 짧은것 같아요. 좀더 자세한 사용법 같은게 있는데 제가 못 찾은 건가요?
https://developer.apple.com/documentation/swift/partialkeypath

Apple에서 제공하는 documents가 너무 간단하고 빈약한거 같은데 저만 그런가요? Object-c를 거쳐서 왔어야 하는건가요? 

KeyPath에 대해 알아보다  PartialKeyPath설명이 나오길래 보게되었는데 PartialKeyPath 쓸일은 별로 없나요? 또 KeyPath는 ios개발하는데 자주 사용하나요?