I think people are reading rather too much into the phrase "sourcing". Read it as "assumed he'd probably wind up marrying a coworker" and the boss in question is just observing the obvious - workplace marriages are quite common in Japan, especially considering that company employees around that age tend to socialize a lot within the company.
One can think of such things as non-pecuniary benefits of a job but I think you'd be hard pressed to find a boss who's ever considered it in those terms. More likely they're just acting on the "truth universally acknowledged" that young single employees must be in want of a spouse.
(Of course, the reverse of this is one of the ways Japanese companies are rough on women - if you're 23 and single people will tend to assume you're going to marry someone and quit in a few years, and treat you accordingly.)