Some might, but many do not. Constantly burning out, knowing that you're underachiving (even if other do not see it) and struggling with handling it all can and does make people end up depressed, extremely anxious and even suicidal. If one doesn't get the help they need, many doors can close even permanently.
I don't think that's the premise of this post.
I think the post is talking about people struggling with adhd, who's symptoms & struggling are being ignored just because they've somehow managed to keep up good grades.
They might also be "gifted" which helps with getting good grades up until some point when it all falls down, as it all just is too much. Also the responsibility and work on other areas of life start requiring the limited capacity to focus and execute necessary home upkeeping, studying & all the other things in life.
Getting the needed medication or even just the diagnosis and the understanding of oneself that comes with it can save a person from a lot of unnessecary suffering.
I probably would have been better off maintaining Vyvanse into adulthood, but I quit taking it as soon as I had the ability to make the decision to. I felt dull, emotionless, my appetite sucked. Yes, ADD sucks and it has caused issues in my personal life, but I am who I am and I accept those parts of myself. Would my grades have been better in college? Would I have been better at maintaining social events? Sure. But sometimes you just have to build good habits to overcome whatever you can.