The way it used to work is that tech journalists (or sports journalists, or any other type) had contacts in the industry. If those people were not directly involved, they probably could at least suggest someone else who might know. Leads were followed up, and eventually the writer got the story.
I'm not sure how it works now, cynically I would suggest that the writer asks an LLM to write the story, gets a rehash of Wikipedia and other sources, and they maybe makes some attempts at firsthand verification.
That is neat, but Scott Chacon is not a journalist, does not act like a journalist and what you are reading is not tech journalism.
You are reading the personal diary of someone with personal connection to a topic and complaining that it is not up to the standards of professional journalism.
The linked article doesn't claim to have insight into the inner workings of the Google Code team, or what Google's leadership hoped to accomplish with that product.
Rather, he is comparing the actual released products.
Specifically, he says that competitors to Github had no "taste", which he seems to be using as shorthand for "making a polished product and really focusing on developer/user experience."
You don't need to interview the folks who worked on Google Code to make that claim, any more than I need to interview Steven Spielberg before I comment on one of his movies.
(Based on my memories of Google Code, I'd say the linked article's observations about Google Code are also absolutely correct, although that's really beside the point)
I'm not sure how it works now, cynically I would suggest that the writer asks an LLM to write the story, gets a rehash of Wikipedia and other sources, and they maybe makes some attempts at firsthand verification.