I have ADHD myself, so you're not telling me anything I didn't know. Rapid-fire media consumption cannot create the genetic condition, but as you said it can create the symptoms. And that's the important part anyway: a generation that has trouble paying attention to important things because they're getting habituated to rapid-fire video formats. Even if the symptoms (chasing the next dopamine hit) are only acute and not chronic, as long as people are addicted (behaviorally, not chemically) to phone screens, those acute symptoms will occur so often that they might as well be chronic for all practical purposes, because more often than not, people will be in that slightly-dazed state caused by coming off the addictive behavior. (I used to have that myself after a multi-hour gaming session, before I realized that I was displaying all the signs of addiction and quit computer games cold turkey. So I know what it feels like.)
I used to think doomscrolling broke my brain before I was diagnosed. Later I realized I was "doomscrolling" way before I got my first digital device, rereading the same fiction books late into the night.
I can buy the argument that rapid-form media consumption acutely creates symptoms like ADHD (for at most a few hours after exposure) because I see it even in NT people.