See bugid 4118429, as listed in the "see also" field.

Basically, The fact that closing a socket's input stream closes the
socket itself is (a) undocumented (b) contrary to normal expectations
of an experienced network programmer, (c) not going to change.

Ergo, I think this needs documenting. (Similarly for the output stream.)
Javadocs as well as other places such issues will matter (tutorials etc).