Masked tables: Bug in documentation

From:
http://docs.astropy.org/en/latest/table/masking.html#masking-and-filling

In this example in the documentation why is there anything masked on output in column `a`? As far as I understand it it should just say `2` there.
```
>>> t = Table([(1, 2), (3, 4)], names=('a', 'b'), masked=True)
>>> t['b'].mask = [True, False]  # Modify column mask (boolean array)
>>> print(t)
 a   b
--- ---
  1  --
 --   4
```
I am not quite sure what the relation to #746 is: If this part of the documenation is tested, then how can this happen? If not, then why is this part not tested?