(having never tried either)

I play a lot of video games in general and both of these games are in a small niche of games that really try to get you thinking. They also tap into what’s great / native about the medium -- e.g. puzzles as constructivist learning devices I’ve personally never understood why most games focus on things like story, movies / books IMO are way better at linear story telling (I know some games do nonlinear stuff which is more interesting at least / unique to the games medium!)

but neither of his games are “fun” in the traditional sense (I play some of those FPS games that are more couch-relaxation types).

As for "mind-expanding" — again, very subjective — I felt that about Braid more than The Witness, but Braid came out at a time when the definition of "game" was much more restrictive than it is now and did a lot to push that definition. (I also have some headcanon about Braid's secret ending actually being about Blow's personal discovery of the concept for Braid and the ramifications thereof in terms of his life and career, and that makes the game more "interesting" to me as a fellow creator, but I digress.)

Much like a good piece of experimental cinema (or psychotropics, or what have you), what you get out of the experience will be colored a lot by what you expect to get out of it, what cultural context you're in, your preexisting familiarity with the thing, and so forth. So you might "get more" out of Journey, or Antichamber, or Passage, or What Remains of Edith Finch, or The Beginner's Guide, if you haven't heard anything about those games but have heard a lot about Blow's games and are just broadly interested in seeing what video games have to offer as a medium for conveying new kinds of narrative / experience.

Though I don't think about it or feel it in terms of "player's time", but I felt kind of respect to my intellect from the game. In particular I was surprised and excited there's no tutorial text anywhere in the game. And really no guidance. I feel all the discoveries as my own. Even if I was nudged toward them by overall game design. 🙂