Think of the times when you're using an unfamiliar api, and your browser tabs are split between documentation and stackoverflow posts. Eventually, you get something to work. If you just clean your hands, and say "I'm done", you've fallen into the trap that the article talks about.

You might look at the code occasionally, and think "maybe I can clean this up?". However ,after a few minutes, you realise how much you don't understand what's going on. So you leave the code, in a sort of superstition - it works after all.

After a few years, when you need to finally modify the code, you've got a problem. The code works, but you never took the time to understand why it works. If there were any superfluous calls, or side-effects that you don't want now, you'll need to take the time to understand how it all works. If you took the time to understand it originally, and wrote a few informative comments, you might have saved yourself hours of work.

It must be said though, occasionally you do need to go deeper with your thinking. To figure out why some bug is occuring, or maybe some complex performance issue. So it is important to have some knowledge of how it all fits together, even if you don't need it all the time.