I think the second answer is closer to the meaning in your quote. In the parable, the wheat and tears are so mixed together and are somewhat similar, so that they need to wait until harvest time to be separated from each other. I think the author is getting at the idea that this is a mixed up world, and it is sometimes difficult to judge the right and wrong of a situation.

"Tares" is a type of grass that looks like wheat, and as a result it is difficult to distinguish and separate the two. In the Bible there is a story (a parable) about the powers of heaven separating the wheat and the tares on the final judgement day.

From Wikipedia: The Parable of the Tares (also known as the Parable of the Weeds, Parable of the Wheat and Tares, Parable of the Wheat and Weeds, or the Parable of the Weeds in the Grain), is one of the parables of Jesus, which appears in Matthew 13:24-13:30. The parable says that during the final judgment, the angels will separate the "sons of the evil one" (the tares or weeds) from the "sons of the kingdom" (the wheat). It follows the Parable of the Sower, and precedes the Parable of the Mustard Seed. According to the common interpretation, the good seeds are the spiritual children of Jesus Christ and the weeds are the rest of the population of the Earth that are the spiritual children of Satan. LINK: https://en.wikipedia.org/wiki/Parable_of_the_Tares I think, and this is only a personal interpretation from a small window into the text you are reading, that the author wants to separate those aspects into good and bad but also that the parts are separated by their qualities and not just randomly. I think though more of the text would give a fuller picture/meaning.

Thank you all very much indeed