What’s the difference between cracked and coarse rounded black peppercorns?
When I have seen this done, the resulting product is in one of two states:

1) The peppercorn is broken down even less than a coarse grind (mostly intact) 
  2) The peppercorn is broken down into rough pieces, the same as a coarse grind

In some ethnic dishes, I have cracked peppercorns just enough to allow the flavor strengthen.  This has given a suble to distinct flavor, in my experience.  This is method 1.

In other dishes, such as a nice steak or a curry, I basically gave the peppercorns a coarse grind -- this leaves pieces you can still eat easily, but gives a much more pronounced flavor.  This is method 2.

In the end, I think the recipe and the instructions will help to determine whether the method is being used to accomplish a coarse grind, or merely exposing more surface area to give a subtler flavor.

YMMV