Absent observation, then sure, one could make that argument. But -- and again, I'm not claiming robust evidence or anything, just anecdotal observation -- I haven't observed this to be the case. I've personally never seen hyperstimulated toddlers get better at self-directing their focus. Entirely the contrary.
Which, surprisingly, is an element of ADHD behavior. Seriously. Apparently a person with ADHD who in conversation is talking about A, if there's a digression will be sure to get back to A to finish their disquisition on the topic.
Actually, having grown up with ADHD and having an ex and 2 daughters with ADHD I can tell you this: We can all hyper-focus on things of interest. But only things that interest us. Attempting to get us to focus on things that are meaningless to us, no matter how meaningful to you or the world at large, no matter how important for our coursework or work, if they don't mean anything to us, we have a much worse time than the average non-ADHD person focusing on it.
I cannot say explicitly that all ADHD people have this trait, but having done a lot of reading and attended a lot of counselling sessions on it to learn to cope with children having it, it appears as though we're not alone in this. It's fairly common for ADHD kids to be able to hyper-focus on topics of interest.
My topic of interest from an extremely young age was figuring out how things work, making them work and making them work better. It's no surprise therefore that I ended up as a programmer.