I apologize for the condescension. I just think these are concepts worth knowing and that they shouldn't be looked down on so much. A lot of people are never going to learn this stuff if they dismiss it so quickly. And that holds back not just themselves but anybody they work with who does understand this stuff.
One of my favorite quotes about software development is that the hardest part of it is not being clever. The flip side, though, is that even the simplest things can seem clever to those who don't have the same breadth of knowledge. In this case, Harry had a solution that seemed clever, but really wasn't that crazy at all. None of his colleagues understood it, but they should have, because it was actually extremely simple.
What's ludicrous about Harry's account isn't his solution or his notion of "adding" employees. It's that he understood these concepts and still took a day to put it together (or that he completely glossed over the more obvious approaches). He wasn't productive at all.
Anyway, as for the terminology, it's just a common name for an associative binary operation on a set with an identity element. If you've never seen it used in this way, I agree that it can seem bizarre, but the more you think about it the more you'll realize it is in line with a generalization of the sort of addition you do on integers.
