[ethikal]

I think the author is writing under the assumption that there are diminishing returns as one gets better at a skill, when really the opposite is true. The number of topics you can absorb per unit term obviously increases with your pre-existing competency with the skill.

There absolutely are diminishing returns in mastering a skill. For example, if you spend a year learning how to play the piano, you might be at a level where you can play some pop songs and impress your friends. To be at the level where you can play some Rachmaninov will probably require an order of magnitude more time (10 years), even though you know all the basics. In the process of mastery from years 1-10, you won't unlock an order of magnitude more songs that you can play as a result. In fact, each year that you march towards mastery, there'll probably be less and less songs that you'll be unlocking as a result. Your returns are diminishing.

This isn't to say that you shouldn't seek to master something (or several things), only that if you are trying to accomplish something which requires mastery of a lot of skills (like starting a company) you should eliminate blind spots by learning a bit about what you don't know. Even reading a book about sales is better than not knowing anything at all about it. Even if you have a sales expert on your team, it helps to empathize and know what they'll be thinking about as you build the product (if you are an engineer). Being an entrepreneur is all about being well-rounded.