Some of them do very simple things—jotting a few key references on the back page, or writing intermittently in the margin—but none of them implements any kind of consistent practice like the one described in Write about what you read. It’s not that they’ve so deeply internalized and automatized those practices that they seem invisible: they’re just not doing those things.
They’re all expert readers, though, in their own way. They read for a purpose; they discuss what they read with others; they use what they read as part of creative projects; etc. So they’re not more effective than other readers for no reason at all.
In fact, the negation almost seems true: most note-taking fanatics seem to actually be quite ineffective thinkers. This should give one pause that it’s important to Write about what you read! I suspect that the key issue here is “Better note-taking” misses the point; what matters is “better thinking”; such people are focused on “better note-taking.” People who write extensively about note-writing rarely have a serious context of use.
My Twitter thread on this note: Andy Matuschak on Twitter: “One way to dream up post-book media to make reading more effective and meaningful is to systematize “expert” practices (e.g. How to Read a Book), so more people can do them, more reliably and more cheaply. But… the most erudite people I know don’t actually do those things!”