Yes, Ola got it right to such extent I even had to copy the title of his post.

In short, the frustration of dealing with businesses unfamiliar with delivering 'project style' can be overwhelming. Anyone recognize the person rushing in and demanding a feature to be added to the top of the priority list? This feature claiming 2 weeks of development time where there are only 3 left.

Usually, when you initiate a project, you already have a sufficient list of requirements. These will usually do and you really don't need more to fill out the time. Instead, you will kick off by prioritizing which requirements get booted from the top of the list, rather than what previously unknown (good-to-have) features that should be added.

As a PM you will meet each additional request with a smile and and gracefully state that you will be happy to add the request to the feature list for the next release. You should currently be in the process of removing requirements that should not be on the top of your list.

By arguing for removal, you get a good understanding for the business case of the feature. If a stakeholder manages to defend the requirement in a way that you keep it on the top of the list, you will also understand the benefits of implementing and and you will not have to go back and challenge it again throughout the project cycle.