Seems like it was never digitally stored in the first place, and the printed text was barely readable due to age. Not really a big win for paper.
The idea that it never existed digitally is obviously untrue. Likely poor wording in the author's part. They probably meant something like, so old that a printout is all that survived (which sounds vaguely like not being digital to someone in an era so far removed from a time when programs were/could realistically be printed.)
Well it had to have been on disk or tape at some point. It wasn't all typed in by hand every time they needed to build a new version.