I have never worked on any reasonably large Java/C# code base. But it C++ once amount of entities grows large enough clear interface overview in header files is basically only way to get familiar quickly with sources.
This is a job for the *documentation* and if documentation is automatically generated (which it is, see '-D') then this argument is moot.
I don't think it will matter at all. As it was mentioned, usage of such feature tends to be private business of certain project - it won't propagate to yours if you don't use it.
Except when dealing with books, tutorials, third party libraries, pull requests, etc...
I dismay.
