If you write an essay about each thing you come across, you'll have to learn the stuff to some depth. That of course takes time, so there's fewer things you can learn about in a given time.
OTOH one can also take the view that learning things properly enables more learning of higher concepts that depend on knowing your stuff properly, and so actually taking your time makes more learning possible.
> If you write an essay about each thing you come across, you'll have to learn the stuff to some depth.
I took the author to mean a much more active pursuit when they spoke about learning — applying the technique to the stuff you're consciously trying to understand better, rather than just any new info you come across.
That said, the depth/length of "write about what you learn" could be tailored to how much weight you want to put behind it — writing could be as little as a thoughtful comment on HN or a tweet as well as a blogpost/essay.
If you write an essay about each thing you come across, you'll have to learn the stuff to some depth. That of course takes time, so there's fewer things you can learn about in a given time.
OTOH one can also take the view that learning things properly enables more learning of higher concepts that depend on knowing your stuff properly, and so actually taking your time makes more learning possible.