Oh, I see what you are talking about. Now, the reason is that

```py
>>> Matrix(...)
```

gives the 2D form, but

```py
>>> print Matrix(...)
```

gives the 1D form (this is just copied from your pull request). The reason is that the former calls the printer, and the latter calls `str` (ultimately, the difference is that the printer calls `repr` instead of `str`, since that's the standard way doctests work).