This was my story. I wouldn't even say I'm particularly "smart", just clever enough to not need to work very hard at much until late high school. BC calc kicked in, all of a sudden I was failing a class for the first time. College kicked in, all of a sudden I was getting low grades even in my strengths. It took a year of that before I even learned the most rudimentary patterns of studying and practice, and over a decade (still learning) to bake those patterns into my day to day behavior.
What makes me very sad, as a slightly tangential note, my university had covered grades first semester freshman year. This let me do terribly, learn from that experience, and not have it impact my future prospects. They've since removed that, and I honestly feel sorry for new generations of students to have one less helpful safety net. With a good support system in place to help recovery, the chance to fail (in a scenario that would be "non-terminal") has been critical to my learning to suck less across the board.
I think you've come upon the laziest conclusion possible. I was one of those smart 'lazy' kids & my poor performance in school wasn't in any way due to being lazy, rather it was due to not caring about school. By middle-school I'd figured out grades don't matter. My parents made too much for me to qualify for college scholarships and honestly, I didn't need scholarships anyway since money wasn't remotely an issue in my family. I simply needed to ace one test.
Because I knew grades didn't matter and that college was covered I didn't do the work, not because I was lazy, but because it was busy work & I had better things to do like running a regional BBS, cracking software, and writing demos in 6502 assembler.
I'd argue that they pretty clearly are different, if you're talking about generic laziness-as-a-quality versus subject specific laziness.
Someone who isn't interested in school might be willing to work very hard at improving in a sport, or work very hard on their extracurricular club, or work very hard to teach themselves assembly and programming, or to learn a musical instrument. They might even be willing to work hard to teach themselves math, but be uninterested in putting effort into math class.
I guess it depends on if you consider "laziness" a universal character quality or not.
Despite having agreed with you above, I'd agree with the dissenting post here as well, that while not caring about something can lead to being lazy regarding it, they are not intrinsically the same thing. I care about my house, but I'm still lazy about getting on the roof and cleaning the gutters. I don't care about many of the jobs I've held in the past, but have still done the day to day work to the best of my ability because professionalism. If we're looking deeply at psychological cause and effect, there may be some utility to examining whether the outcome roots in one or the other. (for me it was both)
What makes me very sad, as a slightly tangential note, my university had covered grades first semester freshman year. This let me do terribly, learn from that experience, and not have it impact my future prospects. They've since removed that, and I honestly feel sorry for new generations of students to have one less helpful safety net. With a good support system in place to help recovery, the chance to fail (in a scenario that would be "non-terminal") has been critical to my learning to suck less across the board.