I like how the OP opens with the query of trust, and then immediately goes into an evaluation of the length of delivery, as if one had anything to do with the other. Several other folks have made disparaging style-related comments. Style isn't a trust issue.
If appreciation of style was a trust issue, I would buy everything Ken Hackathorn and Mas Ayoob sold and ignore everything from Clint Smith, Jerry Miculek, and several others whose style I don't particularly care for. However, style really should not be your basis of trust. If it is, then you are likely making some decisions on a flawed basis.
The OP then confuses the issue between the opening title of whether S&W should trust NnF or if he should trust NnF. These are two completely different issues all together. On the former, it isn't so much that S&W trusts NnF as much as S&W feels like NnF does a good job of promoting their product, plain and simple. S&W has made their their decision for their reasons.
So we get around to the truly salient but otherwise not actually stated query of what qualifies a person as a reviewer? That is a good question, but being qualified does not necessarily mean being trustworthy and vice versa. After all, Gecko45 was founding member of IDPA before going over the deep end or Gabe Saurez was widely trusted before his fraud conviction. Does being a pistol competitor qualify you as a reviewer? How about being a cop? Does running a gun forum qualify you? Does being a firearms instructor? What about "in country" experience? I know a guy with 4 years of "combat experience" in Vietnam that never fired a rifle at the enemy. He was on a Howitzer crew and then command. Is he qualified to review holsters and rifles and such?
One of the common posts I see are endorsements from normal folks of big name people where they say, "If it is good enough for ________, then it is good enough for me" where _________ is some person or agency. That is putting a lot of blind trust into that person or agency and assumes that the product in question is being used in a manner, cared for, etc. in a manner that we would, by people with similar abilities as us, and that just isn't the case. We are most likely nothing like the big name reviewers in terms of skills, lifeways, and jobs. So why would we assume their endorsements fit our needs?
It is like I tell my wife about her nav system, "You have to be smarter than the GPS." Well you have to be smarter than the review and the reviewer. It is up to the consumer to fact check. It is up to the consumer to understand biases of the reviewer. It is up to the consumer to understand if a given product being reviewed or endorsed really fits the consumer's needs.
I am not the biggest fan of NnF's review style either, but there is some good information in his reviews that is very helpful. I like to look at the popular reviewers, expert reviewers, and I especially like the Average Joe reviewers and while the Average Joe reviewers are often the goofiest, most ignorant, and least skilled of the reviewers, they often have more in common with me than the likes of Ken Hackathorn, NnF, or Clint Smith. These are the guys that usually buy their own gear, maintain their own gear, and don't have any sort of endorsement biases (though they are often still quite biased in other ways).
I count on all reviews being biased or otherwise problematic, at least relative to my specific needs and my needs likely are not your specific needs. In the end, I worry a whole lot less about whether or not the reviewer is qualified to review a product and a lot more about whether or not I am qualified to make an informed and properly evaluated purchase decision because in the end, it is my money being spent by me.