Ok, no problem,
The process is automatic, and can not be changed. According to the controller that measures more or less 1 meter with 85 centimeters, the data of step height is already defined and no access to the change to be customized.
Now the problem is that rocks are created with the terrain painting system, and the model has different options of collision system, so the one option of collision compatilbe with step height is the collision type box.
And that's when you climb the rocks without problem.
Step Height Documentation.