I believe it’s not part or whole, it is part AND whole.
Where the emphasis lies depends on many factors:
– beginner or advanced
– time of the season
– weaknesses and strengths
– purpose of the training session
Don’t get lost in drills, I have known athletes who could do drills very well, but performed poorly while running the hurdles. Still drills are an important part of hurdle training. But as always, the proof is in the pudding. Running the hurdles is essential.