As the article goes into, I think you're conflating "NPR" with the stuff that airs on public radio stations in various cities like Boston and New York--much of which programming is also available as podcasts. Thus Radiolab for example (which certainly qualifies for audio-documentary experience) is produced by WNYC and is not NPR.

"NPR" gets used as a shorthand for a lot of the programming that touches public radio stations (or that is created by people who are/were associated with public radio)--I do so myself--but it's not accurate.