That sounds a very strange expectation. Most of my life post university I realized most of questions have complex answers, it is never as simple as you expect.
If the author would check how things biology and medicine work currently, I think he will have even more surprises than the fact that counting populations is an approximate endeavor.
I find the complication comes from poor definitions, poor understanding of those definitions, and pedantic arguments. Less about the facts of reality being complicated and more about our ability to communicate it to each other.