Reading the article, it seemed to me that the kind of learning that it encouraged was more about curiosity, or keeping yourself out of a rut, rather than in-depth mastery of a specific subject or skill. The successful leaders I can think of are less about going deep (that's what they hire people for, after all) but going broad enough to understand a lot of different people around the organization and to keep an eye out for opportunities that the organization hasn't invested in yet, and bring in the right people for those. So, for instance, when Twitter was a new thing, the interested leader might read some articles on it, perhaps sign up for an account and follow a few people, etc, get an idea as to the tone of the communication and who's using it, and then tell his marketing team to investigate further; he's not making himself an expert in Twitter communication (but his Marketing director had better). As opposed to waving a hand and saying, "I just don't get these young people and their tweeting" which is the kind of thing I have heard from some of the older members of my field... Do you really find that you are incurious about the world? (That's not sarcasm, it's just that that's a different issue than "I have trouble sticking with something until I master it").
In terms of learning in general, it might be that you don't respond well to traditional text and classroom based instruction, or you might not need to truly master every new skill. You don't have to do everything in depth...a lot of times when I decide that I want to learn something new and the project peters out, it's because I really only needed to know a little to meet my goal.
And in terms of "loving your job"--I think a lot of people use this to mean "I really like my job and am good at it" rather than the "I have a passion for my work" that gets a lot of scorn around here. I think very few people have a passion that matches their paid employment, but I truly believe that a job you like and can succeed at is an achievable goal. Cal Newport has written a lot on the subject and his comments parallel what you say about your acquaintance the project manager.