Org Babel resolution of `:var` value reference inconsistent

[myq <myqlarson@gmail.com>]

Sometime since Org version 8.3beta and now, the way Org Babel resolves
the value of the `:var` header argument when assigned to a reference has
changed.

Previously, the following would work when exporting:

--8<---------------cut here---------------start------------->8---
* test

#+BEGIN_SRC R :var dat=table-data
  print(summary(dat));
#+END_SRC

** COMMENT

#+TBLNAME: table-data
| number | measurement |
|--------+-------------|
| 1      | 10          |
--8<---------------cut here---------------end--------------->8---

The above /still/ works when manually evaluating the block (C-c C-c whil
in the block), but when exporting, the following error is thrown:
`org-babel-ref-resolve: Reference `table-data' not found in this buffer`

Curiously, the following tweak works for both manual evaluation and for
exporting and produces the same results that the above file used to
produce:

--8<---------------cut here---------------start------------->8---
#+OPTIONS: inline:nil
* test

#+BEGIN_SRC R :var dat=table-data
  print(summary(dat));
#+END_SRC

*************** test
#+TBLNAME: table-data
| number | measurement |
|--------+-------------|
| 1      | 10          |
*************** END
--8<---------------cut here---------------end--------------->8---

This seems to be a bug, but perhaps there is a reason for this new
behaviour?

Thank you in advance for any insights.