I agree. An adult can ask themselves what they're doing and why and how it aligns with their interests so on (aka have that midlife crisis, haha), a kid probably doesn't yet have enough self-reflection capacity yet.
In my perception, distractions are ideally managed through interest management. Make the desired task actually truly desired - and you're guaranteed to not get distracted. And in an ideal environment, there should be an educator overseeing a kid and asking what went wrong if kid decides they wanna play with their phone instead of working.
When you don't have someone to help with "why am I doing this and not that?", I guess it's true that next best option is to eliminate potential of distraction. It's not great, but is probably better than not doing anything about it.
So, as always, there is an ideal approach (that doesn't work because it requires ideal environment), and a working approach that's very contrary to the ideal way of doing things.
Hm... Maybe teaching kids (and adults) about the modern attention/spam economy actually works can help to lower the distractions. After you see through attention-grabbing tricks, scrolling through online feed wastewaters (or watching junk on streaming platforms, or playing "games" whose entire raison d'être is to make money on players) becomes much less interesting or rewarding. Just a thought.