I always take great care to not use the word "plot" when talking about adventures and campaigns, because that word really means "step by step structure" in all the many uses it has. However, Cook did not and used it in the paragraph in which he pretty much explains sandbox play. (In quotation marks, but still.)

But I do find it quite astonishing that B/X frequently shows up as a system of choice for both very straightforward dungeon crawls by the book, and for very story-heavy adventures and settings (Lamentations of the Flame Princess, Spears of the Dawn). It's very versatile and a great allrounder. Which I think probably comes from it being a very lightweight system. It leaves a very large amount of room for handwaving and puts very little restrictions on what kind of waving you might want to do while still staying very close to the rules as written.