This is ahistorical. iPods were locked to a specific iTunes library at a time when other players acted as mass storage devices, drag and drop.
DRM-free didn't happen until after the iphone [0]
iPod was a better product with better marketing, but it was not freer (libre) than its competition. (Personally I liked my creative Zen with Yahoo unlimited subscription [1]- DRM was a feature! Spotify wouldn't come along for another 5 or 6 years)
[0] https://www.theguardian.com/technology/2009/jan/06/apple-dro...