Do you get REPL? Do you get debugger?
Notebooks are between REPL and "proper code" on this spectrum. They can be used even when nobody else sees the results. They are useful for experimentation, to figure out things you don't know you don't know as an extension of your working memory. They are less temporary and disposable as REPL but less reusable than proper code. Another example is Org Babel in Emacs.
Jupyter notebooks in the article are used for "learning-oriented tutorial" or "goal-oriented howtos" docs. You see explanation, code, results, and it is easy to try it. There are solutions with a single click that can get you the running editable copy.
Misleading docs may be worse than no docs, so using notebooks as executable documentation is a plus. Though it is not the best format for e2e tests in general. Tests may be too complex for that. Software (proper code) is better at handling complexity in the general case.
Jupyter notebooks in the article are used for "learning-oriented tutorial" or "goal-oriented howtos" docs. You see explanation, code, results, and it is easy to try it. There are solutions with a single click that can get you the running editable copy.
Misleading docs may be worse than no docs, so using notebooks as executable documentation is a plus. Though it is not the best format for e2e tests in general. Tests may be too complex for that. Software (proper code) is better at handling complexity in the general case.