In my opinion, there are many advantages to applying the content first approach.
Firstly, it leads to minimalistic design and better user experience. The whole design based on the required information and interactions which the user would need to achieve their goals. Apart from that, even designers would be happy to figure out the bare minimum of elements, components, features that are necessary for the successful design. Because it would force the team to agree on the content before drawing up clickable wireframes, or even before making UI elements.
Secondly, the most critical step (more critical than the previous one) is to understand which content might be set into the design. To figure out that you should ask a series of questions relevant to the product requirements that started with the question words like What? Why? How? For whom?
Then, thinking of the pain points that potential users struggling with in everyday life, observing how they are solving they are solving their problems without the upcoming product, at the end speaking with the target audience and summing up all feedbacks into needed information for the content.
But this content “first” approach can only strengthen the final “outcome” of the project you are working on.
If you understand how the “outcome” (user flow) should look like for the content of the first user story, then begin writing it and testing it with the interactive prototype to validate it. On top of that, the more final the content structure, the more you will be able to evaluate the correctness of the user story for the product.