Learn and get paid for it asap. Learn what your client/project/employee needs and everything around it - this is the fastest and most rewarding way.
However, there are several studies[1] that show dramatic improvements in retention and understanding from material vs. just studying it. So if you consider retention and understanding to be the goal outcomes of learning, forcing yourself to structure your thoughts about the material enough to communicate it with others has clear benefits to learning rate.
[1] Example: https://www.sciencedirect.com/science/article/abs/pii/S03614...
What definition are you referring to, because that statement doesn't make sense.