I don’t think your comments are in conflict, being engaged with an interest does not necessarily mean being directly engaged with a project/task related to that interest. I definitely empathize with the scattershot approach being frustrating, but i think that comes out of an intense interest in a topic, and a lack of ability to focus on a specific task, even if it is self-selected and related to an interest.
I can think of many examples of times where I was unable to complete a project (in part) due to a drive to answer every question that I encountered in the process, and questions branching from those answers. So yes it does definitely impact productivity and perseverance for specific tasks, but I would separate that from the unique ability to learn intensely about interesting topics with reasonable depth and exceptional breadth that ADHD seems to give.
I can think of many examples of times where I was unable to complete a project (in part) due to a drive to answer every question that I encountered in the process, and questions branching from those answers. So yes it does definitely impact productivity and perseverance for specific tasks, but I would separate that from the unique ability to learn intensely about interesting topics with reasonable depth and exceptional breadth that ADHD seems to give.