I work as an editor sometimes. I've worked in technical writing, though not specifically science journalism.
My guess for why this keeps happening, is that it's a two-step process, fueled by a failure of communication:
1. The science writer themselves does understand epigenetics — but doesn't think it's important to the point the article is making for the reader to understand epigenetics. The writer wants to remove the requirement/assumption of "understanding epigenetics" from their writing, while still being technically correct in everything they say. So they choose to gloss an epigenetic change as "causing changes to the DNA." (Which it certainly does! Either chemically — to the DNA molecules themselves, through methylation; or structurally/topologically — through modifications to the histones around which the DNA is wrapped.)
2. The science writer's not-so-scientific editor comes along, doing a stylistic editing pass; sees the word "DNA"; and says "hey, that's jargon, and we're aiming for accessibility here — we need to replace this." And they (incorrectly) decide that a valid 1:1 replacement for "DNA" is "genes" or "genome."
This invalidating change could be caught... if the publication had a formal workflow step / requirement for the editor to perform a back-check with the original writer after copyediting + stylistic editing, to ensure that validity has not been compromised. I believe that big-name science journals and science magazines do tend to have these back-check steps. But smaller publications — like the PR departments of universities — don't.
My guess for why this keeps happening, is that it's a two-step process, fueled by a failure of communication:
1. The science writer themselves does understand epigenetics — but doesn't think it's important to the point the article is making for the reader to understand epigenetics. The writer wants to remove the requirement/assumption of "understanding epigenetics" from their writing, while still being technically correct in everything they say. So they choose to gloss an epigenetic change as "causing changes to the DNA." (Which it certainly does! Either chemically — to the DNA molecules themselves, through methylation; or structurally/topologically — through modifications to the histones around which the DNA is wrapped.)
2. The science writer's not-so-scientific editor comes along, doing a stylistic editing pass; sees the word "DNA"; and says "hey, that's jargon, and we're aiming for accessibility here — we need to replace this." And they (incorrectly) decide that a valid 1:1 replacement for "DNA" is "genes" or "genome."
This invalidating change could be caught... if the publication had a formal workflow step / requirement for the editor to perform a back-check with the original writer after copyediting + stylistic editing, to ensure that validity has not been compromised. I believe that big-name science journals and science magazines do tend to have these back-check steps. But smaller publications — like the PR departments of universities — don't.