Do you storyboard your video shoots? Do you sketch out a presentation? That is what XD is for, that design phase of an application before the costly investment in connecting to those databases, dealing with all the states that an app can be in (form errors, data issues, etc, etc, etc). It is meant to make sure the flows from screen to screen are right and that the layout works on mobile screens. You can skip the design steps and just start coding, but I would be willing to bet that the results will not be what you expect.
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