3.4 only gets security fixes.  3.5 only gets bug fixes.  Feature changes ('enhancements') are limited to future versions.

This is not a behavior issue because the code and doc match.  https://docs.python.org/3/library/io.html#io.FileIO.name says (as Martin paraphrased) 

"name
    The file name. This is the file descriptor of the file when no name is given in the constructor."

As I remember, this was discussed when io was designed.  The alternatives to name = fd: no name attribute, name = '', name = None.  All are about equally easy to test, as long as the decision is documented, which is clearly is, contrary to the claim otherwise.  I believe the deciding factor is that fd has more information than nothing, even if redundant or useless.

In the absence of sufficient reason to break existing code that follows the doc, which we are generally loathe to do, the design change should be rejected.