I don't think most people would use this definition. It covers gambling/lottery winnings, finding buried treasure or a gold mine, and paying someone to file your taxes and splitting the extra deductions they found. Really, it includes employment at large- the only 'non-theft' employment would be that which provides no net benefit to the employer. There are parlances where these are included intentionally and they share a starting syllable, but to the common people this is not a definition of theft.
Why do people keep assuming that employers don't do any work? Management is work. Is an employee stealing if they receive any net benefit from their employment?
