It is because 'in our own society, different segments of the population act out different psychosexual dramas' that Joshua Harris will be following one script and the "world" another.
Which script other I bumped into a friend outside a store at the shopping mall and told him of a chair I'd purchased at a different store.
He wondered how much I paid, so I took a step forward and whispered it to him.
Abraham out of a sincere desire to do God's bidding—to birth an heir—, and from a realistic assessment of what was available for him to work with—the deadness of Sarah's womb—, kissed Sarah-in-bed goodbye to embrace a more workable method: Hagar in bed.
Similarly, Joshua Harris sincerely wants to work into a good marriage as God plans, and he realistically assesses the immaturity of high school dating, so he kisses it goodbye in order to embrace an amalgum of fellowship-meeting interactions and counsel & advice of his parents and elders.