Reason why co_filename is no longer interned?

[David Christian]

In 2005, when the ast branch was merged to head, compile.c

when setting the filename for the code object,
PyString_InternFromString was replaced with PyString_FromString.

http://svn.python.org/view?view=rev&revision=39758

This means that where before, you could rely that
<function>.func_code.co_filename == <function1>.func_code.co_filename

Does anyone know whether this change was purposeful?