Abhirup, Expert Judgement is a valuable commodity to be used in reality, whenever you need some crucial information to help break up some confusion.
Yet, for the exam, and the sake of clarity when piecing together ITTOs, I often recommend to candidates to try to memorize ITTOs. The way the questions are worded on exams, after you've done your best to know the ITTOs, will offer clues within those words leading you to select the answer.
I'm not sure there's one response to directly answer your question, but here's my interpretation. When you're collecting requirements, for example, what are you really doing? You're gathering the facts about what has to be completed to satisfy the customer's demands. This requires interaction between you and that customer and related stakeholders. You've been entrusted by the sponsor so you should have the competence to do a voice of the customer analysis. You can't be going to some expert for every step in a project. I apply this reasoning to the Develop Schedule and several others from the list. It's you and your team that have the responsibility. If you build upon the project initiation steps where expert judgement is used, you've probably set up a base from which to plow through the remaing steps.