z/OS has as much in common with z/VM as Windows does with Linux, so I'm a little bemused why you posted that link.
Notice that the _OE_SOCKETS macro appears in both, and seems to have the same purpose. Which is not surprising, since probably IBM used the same code base for socket support in both products. I did not intend to say that z/VM documentation applies to z/OS, it's just the most similar case I found.
I think it's just a coincidence. z/VM doesn't use the z/OS Language Environment product, which provides the relevant header files used to make socket calls.
This has nothing to do with the the original question.