I'm follow a tutorial to create a low poly environment. So I have to make mountains... I go to Sculpt Mode and activate Dyntopo [ resolution : 7.00 / Refine method : Subditive Collapse / Detailling : Constant Detail] and when i try to do a picks It becomes smooth.
Dynamic topology has an option to enable smooth shading, enabling this turns on smooth shading for the entire mesh.
I had the same problem when following the tutorial. These settings seemed to work for me.