I wonder why journalists don't voluntarily to this? It seems obvious to me that high quality journalism should cite sources and methods, if only to protect themselves from future criticism if their news reporting turns out to be wrong. At least then they can point at the fault publicly, explain how it happened, and what they are changing to make sure it doesn't happen again.
In some cases, they might deliberately not want to give certain sources, but in that case I'd like them to explain their reasons as a footnote of each article.
I suspect citing sources and methods in detail might be considered 'boring' for the average reader if done within the prose of the article.
Perhaps what is needed is a new normal that articles online will have footnotes which are only shown to those who want to see them - that way the body of the article can be short and succinct, with the 'borig' citations in the footnotes.
In some cases, they might deliberately not want to give certain sources, but in that case I'd like them to explain their reasons as a footnote of each article.