I think this is missing a big point of the article - Currently there is a real perception problem that probation (etc) is not enough punishment, therefore a lot

I think this is missing a big point of the article - Currently there is a real perception problem that probation (etc) is not enough punishment, therefore a lot of people get sent to prison. This is actually the same as you're saying. So his solution is to provide a harsher middle ground, that provides more punishment and more "benefits" of prison, without needing to send all offenders to prison. In fact the solution keeps prisons around - partly for the violent offenders in your example, partly for those that don't get the message from the middle ground.