I hear this an awful lot, but either as a manager or IC, I have no idea what it means.
From my perspective, if you leave me alone to do my thing and don’t interrupt me with random shit all the time, I’ll grow naturally. But the manager doesn’t have to be involved in this beyond shielding me from the bullshit, so I guess people are talking about something different.
That's what _you_ want, but it's not what everyone wants. Some people want or need much more active participation in their growth, and it's a manager's job to find what's right for each person. A common failing new managers make (and one I made as well) was assuming everyone wants to be managed like I want to be managed. I was very much in that "leave me alone and let me do my thing" mindset, and that caused a lot of problems much later in life.
Also, this depends on the experience level of a manager's reports as well. If all of them are quite experienced and have clear goals regarding their career, the manager does not have to spend much time on career coaching. They can focus most of their time on coding. But if that is not the case, then they'll have to balance their time accordingly.
That's a good point you make regarding intentional vs unintentional. This point had not occurred to me earlier. After thinking about it though, I am confident that its not applicable for my scenario :0. I will have this in mind for future situations so that I don't come to wrong conclusions.