I just wonder what they mean by "breaking pflug" do they mean defeat it
I assume that it means the same as using the other meisterhau to "break" the other guards per Ringeck's description. I don't know why scheilhau would be an exeception to zwerch, krump, etc. breaking other guards.
The way I was shown you can use low scheilhau to defeat pflug by stepping in, binding, and thrust/strike with the short edge. This is one fluid motion. It seems to work fine. (I'm still a klutz so I don't always execute correctly.)
If the opponent attempts to counter the thrust/strike, e.g. via kron, you can proceed to wind, throw, take, etc.

