I’m a bit of both. I have long-lasting, deep-running, intense passions for many things in life (I’m obsessed with aquatic stuff for example, and I’ll hop in the water with a mask and snorkel anywhere and any time of year if I might see something interesting… And my definition of interesting pushes the boundaries of the meaning of that word for most people), yet I’ve got those fleeting interests as well. Far too many of them for sure.
I’ve done the video game one before. Not coincidentally, it had an aquatic theme. I lasted like 2 weeks. I wasn’t discouraged by a lack of interest necessarily, but the sense that it was truly impossible to pursue.
I know some other people with ADHD who have very central and long-lasting interests, but you’re not wrong that the passing (and often even more intense) ones are real too. Perhaps more common as well.
That’s why I said “some presentations”; some people find a groove that allows them to go deep on something they’re interested in, I guess. But certainly not always.