Yes, I coasted through school until college. Never studied, never had to, even in the gifted, honors, and AP classes. I especially did well on tests. Graduated 3rd in my class, only .001 GPA points from 2nd, with a handful of 5s (and a couple 4s) on my AP tests. Had undiagnosed ADHD (inattentive type) the whole time. Always procrastinated heavily, usually wrote papers/did projects the night before they were due. The closest I got to "studying" was re-reading the chapter I was going to be tested on the morning before the test, and even that was only for social studies classes where you had to remember names and dates. I did not need to study at all for math, science, or English courses. I got very lucky with a handful of
exceptional teachers in high school. Teachers that actually cared about me and my success. I wanted to do well in school, because I got praised for it - both by my mom and by teachers. I craved that praise like nothing else as a child so I always did just enough to make sure my grades stayed high.
Life fell apart in college. Huge class sizes with no personal connection to the teacher and being solely responsible for meeting deadlines and studying eventually ruined school for me. Your lecturer with over 3000 students doesn't give a shit about you or your performance in school. I lost the immediate feedback and praise that I used to get in grade/high school, and with it, my hyperfocus on doing well in school was gone.
I fell into a deep depression, took a year off, took anti-depressants, tried school again but still just couldn't make myself go to classes anymore. Dropped out. Spent a few years working a dead-end call center tech support job. Wound up getting into software anyway (my failed degree was going to be in CISE) and I do well enough for myself now (especially after getting an ADHD diagnosis and getting medicated for it), but college/young adulthood was a disaster for me. I also had to declare bankruptcy in my mid-twenties - another consequence of depression and undiagnosed ADHD. Impulse purchases and the guilt/shame/avoidance spiral turned my credit into a mess.
Most of my peers actually did far better than me (like, they actually finished their bachelors (some went as far as PhDs) and went on to good jobs in the fields they studied for), but I don't think any of them had ADHD. That was the other thing that kept me focused in high school. I was part of a decently sized group of "smart kids" - we would compete with each other on grades, and that competition helped keep me on track. Lost that in college too.
Basically, yeah, giftedness and ADHD are a terrible combo. With ADHD, you need a lot of structure and work ethic to succeed in life, but if you're smart enough, you don't have to develop any of those skills to excel in grade/high school. Then you hit adulthood and everything falls apart.