Community may not claim to be the first with notebooks; but they certainly seem to think they have something nobody else has with it. Per their website, "The Jupyter Notebook is the original web application for creating and sharing computational documents. It offers a simple, streamlined, document-centric experience."
Which, I suppose I can cede that they are among the first "web applications" that do this. But I have a hard time really getting behind a ton of the discussion on it. Even talking about the "breadth and depth" of part of the python community is to ignore how much had been done for years in the mathematica community.
They do say what you quote with those words, but I think their intention is just trying to clarify the difference between Jupyter classic and JupyterLab. The Sage notebook predates the Jupyter project by at least five years, but was visually and functionally very similar.
To be fair, I'm not so worried on this. Even if Jupyter was what introduced some (many?) folks to notebooks, that is fine.
I was soured as early advocates were pitching it as way more impressive than it is. With some being proud of themselves for realizing you can put a "pip install" at the top of the notebook, thinking that somehow made it repeatable. I recall senior engineers wanting notebooks to have prod access so that you could deploy from a notebook. And thinking they were making a good practice statement. Ugh.
Which, I suppose I can cede that they are among the first "web applications" that do this. But I have a hard time really getting behind a ton of the discussion on it. Even talking about the "breadth and depth" of part of the python community is to ignore how much had been done for years in the mathematica community.