So black holes do tend to take on a cylinderical shape in order to increase stability. Galaxies have the same tendency.

As a result matter seems to be ejected from black holes along the axis of the cylinder.

Now the same thing happens from vortices, with one crucial distinction: With vortices, matter is only ejected in one direction. But for black holes, matter is ejected equally in both directions along the axis normal to the 2-d symmetry. That is how astronomers and astrophysicists distinquish black holes from vortices.