Pardon for the offense, none intended.
I do accept what Barbie and Vogt say, but I find that 75% of it always has to be "unpacked". For example, "Mixed blood and DNA", or "40 Knife wounds and bruises", etc. They deliberately write in ambiguous phrases easily lent to darker interpretation or outright misinterpretations. But if you parse what they say, they are playing right up to the line with what they have to work with. They are adversarial, but they do have some level of sketchy "ethics". So no, I don't discount them entirely, but the facts are often hidden in deep husky outer-matter.
On Diaz or CT, if the police won't let them file a report, make them wait around for hours at the police station or refuse to do anything about their complaints, that is not proof that no complaint was ever filed. (I know you'll ask for sourcing, I think I read the CT in Nina's and/or Candace's books, and the Diaz I believe is pieced together from the Graham article (which you also doubt is real?) and other sources I can't pull to memory at this second).
Sources that rely on the same point of reference, I agree (duh) are not reconfirming. Separate additional facts may be emphasized from two writers, yet still come from the same source document, and we'd never know as readers.
So we're always gauging credibility of sources, and hopefully flexible enough to revise accordingly.
Seems to me though, you have to be willing to accept provisionally the research presented by reasonable and responsible writers, journalistic professionals (not like the daily mail that has repeatedly written fictional accounts of court proceedings that never occurred), in order to connect the dots and see a pattern that may exist.
If you are never willing to 'connect the dots', then you certainly minimize your chance of error. But you also minimize your chance of insight. So I tend to favor the 'suspension of disbelief' in so far as reasonably possible, until such time as it's contradicted or feels implausible.
On a past point, when Mignini arrived at the crime scene on the Day One, he was greeted by Napoleone and Lorena Zugarini (looks like the east german swim coach, famous for kicking in the downstairs door window - which as long as I'm musing, would be a good way of throwing extra glass into the downstair apartment in case Rudy had trailed any inside when he went downstairs for a change of clothes after killing Meredith

. Zuggy and Nappy are on the crime scene video greeting Mignini, think I saw it in Vogt's documentary, ironically.
However, even if Guede were not recognized at the earliest moments on day one, MIgnini still had plenty of reasons for framing AK & RS in a group crime,
as he had done in the past and was doing at the time. (I do believe they spotted Guede off the bat, but even if not, the framing issue is still in play, imo).