This old sense is encountered, like in your example, but much more often "fruits" is used in the culinary sense.
Many people perceive your example as a metaphor, the results of the labor being compared with the fruits of a tree, but in reality the direction of the metaphor has historically been opposite, the fruits of the tree being called thus because they were considered the useful results of its cultivation.
I don't know what you mean by that. People do talk about "the fruits of" their labors.