[O] odd behavior for begin_src org :results

[Greg Minshall]

Org-mode version 8.0.1 (release_8.0.1-42-g267cbe @ 
/Users/minshall/usr/share/emacs/site-lisp/org/)

hi.  the following produces #+RESULTS:
----
#+begin_src org :results replace
hello
#+end_src
----
but, repeated evaluations seem to grow the list of results.  e.g., after
four evaluations:
----
#+RESULTS:
hello
hello
hello
hello
----

the following does not produce #+RESULTS at all:
----
#+begin_src org
hello
#+end_src
----

is this intended behavior?  the code thinks so; ob-org.el has:
----
(defvar org-babel-default-header-args:org
  '((:results . "raw silent") (:exports . "code"))
  "Default arguments for evaluating a org source block.")
----
otoh, the manual thinks ":results replace" should be the default:
----
   * 'replace' The default value.  Any existing results will be removed,
     and the new results will be inserted into the Org mode buffer in
     their place.  E.g., ':results output replace'.
----

cheers, Greg