Voluntary vs Involuntary unemployment

Is it possible to have a voluntary recession? Dave Henderson writes about the period immediately after WW2, with high unemployment:

According to official government data, the U.S. economy suffered its worst one-year recession in history in 1946. The official data show a 12-percent decline in real GNP after the war. A 12-percent decline in one year would fit anyone's idea of not just a recession, but an outright depression. So, is the story about a postwar boom pure myth?

But it was voluntary, people preferring leisure over their war times jobs:

If you ask most people who were young adults in those years (a steadily diminishing number of people, so talk to them soon) about economic conditions after the war, they will talk about "the postwar boom." They saw it as a time of prosperity.

How does this reflect on theory?

Simple, major restructurings cause major unemployment, even when the restructurings are expected. This adds evidence to Recalculation. We were coordinated and enthusiastic about post war restructuring, yet still required a short period of unemployment.

What is the real difference between voluntary and involuntary unemployment? It is the expected vs unexpected.