It really isn't "just an idiom" -- DNA holds information even in the very most rigorous definition of information as defined by information theory by Claude Shannon and others. Computing the entropy of sequences is actually a useful way to predict if they are likely to have a function.
information theory equates information with data (bits), it's the spherical cow in a vacuum and in that context the "information" that DNA "holds" is just a jargon referring to the bits.
it's not because "atom" isn't a technical term, it has always referred to the indivisible bedrock (greek root a-tomos or "not-cuttable").
equating information with data outside the context of information theory is precisely wrong and definitely not the same information being discussed in tfa. bits do not comprise information, you could say data reduces to bits. data != information. data is objective by definition. information must be able to inform/influence the metaphorical ledger backing ones ability to know, transferring knowledge. not all knowledge can become information and not all information can become data.
nah I can do better. DNA is just data, you can say it "holds information" the way a footprint holds information but that's just an idiom.
knowing is just a perception. you can think you know something and be wrong.