[jb1991]

It does indeed sound like you have some very old documentation.

(as a sibling comment pointed out, swift protocols are typically used for things that in objc you would use inheritance)

[pjmlp]

Old enough to have enough Objective-C protocols and categories in action.

The kind of documentation that inspired Java authors.

https://cs.gmu.edu/~sean/stuff/java-objc.html

https://en.wikipedia.org/wiki/Portable_Distributed_Objects

https://en.wikipedia.org/wiki/Distributed_Objects_Everywhere

[jb1991]

Quite a lot has changed in objc since the nextstep days! And a lot more changed as Apple learned from that and built swift. My guess is you don’t know these languages as well as you think if you’re not clear about these differences.