I do think it matters, because we are trying to establish some sort of utility of having focus in the context of the conversation. The theory of this thread is that a lack of focus is harmful and, at least partly, to blame for why young people are struggling.
You can be the most dedicated piano player, but if you later decides to channel that dedication into e.g. writing you are very likely to be struggling anyways. So now you are essentially in the same boat as everyone else.
Young people are mainly struggling because education, housing and long term careers are competitive and costly. Of course dedication can help with being successful in almost any sense of the word. But overall it is very likely overshadowed by other factors as e.g. your position in the housing market.
How many people who could afford a mortgage in a major city in their early twenties, by any means, are struggling with their lives today? Certainly a few, but surely a lot less than those who don't yet have a stable home in their thirties.
I personally think learning how to focus and power through a struggle is the important skill to learn, regardless of what form it takes. Finishing 10 imperfect paintings is more of a learning experience than never finishing one perfect painting. Finishing a terrible novel in NaNoWriMo is more important than giving up because your story is bad. Making it through school with a C+ is more important than dropping out because it's too hard. If you're going for a run, the first mile might be excruciating pain but then the runner's high kicks in. Now every time you go for a run after that, you'll know to grin and bear it because the pain will go away and it will get easier.
I'm arguing that it's not what skill you learn, but rather that you did. You moved past something being new and exciting, got to the point where it was frustrating and boring, and you kept going anyway. I'm now wishing I hadn't use a computer as my example because I still feel like you're taking the wrong lesson from my anecdote. I don't credit my childhood computer use for my successful career as an adult. I credit my (forced) single-minded focus, where giving up was not an option.
In this story, my siblings-in-law never knew that it gets easier, never knew that there is a plateau you can overcome, and never made it to the other side. Because they never had to. It's a story about not giving up, not a story about how everyone should learn to use a computer.
I just don't think it is accurate. Often pursuing something means giving up other things, which won't help you not to struggle in life. There is often no plateau in menial or highly competitive professions. Trying to e.g. become a writer will leave you struggling for a long time. Unless some can provide for you in the meantime, which has little to do with your own focus. I just don't think focus as such is that relevant for whether you will struggle or not in life. A lazy programmer is still on average very likely going to struggle less than a dedicated service worker. There are plenty of, say, high school football players who have more grit than most of us but are doing worse in life than the kid who barely knew how to tie his own shoes.
You can be the most dedicated piano player, but if you later decides to channel that dedication into e.g. writing you are very likely to be struggling anyways. So now you are essentially in the same boat as everyone else.
Young people are mainly struggling because education, housing and long term careers are competitive and costly. Of course dedication can help with being successful in almost any sense of the word. But overall it is very likely overshadowed by other factors as e.g. your position in the housing market.
How many people who could afford a mortgage in a major city in their early twenties, by any means, are struggling with their lives today? Certainly a few, but surely a lot less than those who don't yet have a stable home in their thirties.