I think 10 shifts is probably too much to be considered sporadic. He was engaged in providing services for hire, he did it for a profit, and he was basically freelancing in his usual line of work.
One of the key phrases is "engaged in a trade or business." One could argue that if I helped my neighbor repair her backyard fence and she paid me $100, while I am normally a teacher and didn't even want the money, I was not "engaged in the trade or business" of fence repair or "handymanning" and even though I did provide a service for money, it was not self-employment.
Here, though, 10 shifts freelancing in his usual line of work does not sound like it would pass the IRS if audited.
