There's actually quite an involved skill to reading and fully understanding this kind of writing - and it's infuriatingly difficult to pick up that skill (I've been developing it by spending time talking to professional journalists, but I'm still not there yet).

When you read "another person familiar with the deal who spoke on the condition of anonymity to discuss sensitive matters", you need to translate it to something more like the following:

The journalist who wrote this has found a credible source, who has insider knowledge.

That source has requested anonymity, and the journalist finds that request credible.

The journalist then used their skills and experience in writing about this area over the course of their career to evaluate if that source was trustworthy. They also considered if the source had their own motivations which could affect what information they chose to share and why.

The journalist may have then cross-checked that information against other sources of information to help evaluate its credibility. This becomes more important the more high stakes the claim in question becomes.

An editor (and potentially even separate fact checkers) evaluated the statement as well, and applied judgement as to whether it held up firmly enough to be published.

There are so many phrases like this in top-tier journalism. When an experienced journalist reads an article from someone else that says "a senior official in the administration said..." they can often narrow that down to just a dozen or so potential people, based on their knowledge of that beat.

As a non-journalist reading newspapers this is pretty infuriating, because there's this whole language that you need to know about in order to fully understand what's being communicated here.