I think we're getting at the same thing. The time example is used as a comparative generalization that there is a need to focus and understand the fundamentals. The point being that given some period of time, if an average individual chooses to learn 10 languages at once, they probably wont master the fundamentals, compared to mastering those in one language. Of course there is the side case that comparing different languages and their patterns will actually be even more valuable in overall understanding, I would have to side that one first needs a deep enough understanding for that to be an advantage.