That would not have happened. The only reason things moved forward is because he threw up due to the threesome and was caught. Kuroo only had the courage to force him to admit his feelings due to the terrible position they were in and saw him suffering. Without this, they likely would have danced around each other for who knows how many more years. It isnt the plot device I would have chosen, but it's the direction the author chose to go in and the ending would not have worked by deleting that scene
Um, the threesome was unnecessary.