Am I confused? As I understand, cathodic cleaning action happens only during the electrode positive portion of the ac cycle,(workpiece negative as the electrons are leaving the workpiece to jump to the electrode.)

My near new Diversion is a 72%EN or 28% EP, with square wave

I bought a Dialarc 250 HF with water TIG. It being a transformer machine I think AC balance is 50%, with sine wave. It is said to be "high frequancy", though I don't know how high that is. Shouldn't this mean more cleaning action? It doesn't seem to be the case. Is this normal? Can it be fixed?