New Interchange rule for Nab Cup

Does anyone know the reasoning behind the interchange rule in the Nab Cup. My theory is its been introduced to slow the game down and this in turn would reduce the severity of impact injuries. (bit the same as the take 5 off campaign for cars has done).

I hear a few coaches grizzling that it will be dangerous to the health of the players but would that only be if they tried to maintain the pace they are accustomed to without the benefit of extra player interchanges.

I am really only seeking the logic behind it, not necessarily whether you agree or disagree with it.