I don't think I agree with the above analysis. Rather, they all came up with the obvious idea, and then it took them a varying amount of time to produce the videos. Same thing happened to the videos of shooting through rolls of toilet paper.
There are way more than 50 new guns coming out each year. More like 200 of them. Watch TGC if you don't believe me -- Jon announces 3-4 new guns each week. And people do review these "minor styling changes". Remember P365 SAS? Guntubers were falling over themselves for that one! But manufacturers outside of SIG, Glock, and S&W aren't going to send free guns to dozens of reviewers. So the issue is more of financing and availability.
I'm not here to debate who first had the idea of a new gun owner or TP shoot video - or who got the idea from whom - or who had the idea first and someone else beat them to the upload. YT is full of copied ideas and commentary... and commentary on others commentary.
However, if you want to think that production time was the only reason that all these videos came out within approximately a week, I think that you may be viewing people who are in a daily search for views, likes, and subscriptions with too many altruistic qualities. I personally think most took a page out of the Golan-Globus school of film making. Wiki that one if the reference is too dated.
We may just have to agree to disagree the definition of a new gun. Our definitions of new gun vs minor styling changes are different. I'm talking about new product lines and offerings that are novel, significantly different from products already manufactured, not simple variations of the same stuff. If you define the P365SAS as "new", and not just a variation of a P365 with a slide milled Meprolight FT Bullseye, then you might as well count every sku at that point - every product offering in every color, distributor exclusive, and every existing product with a milled slide a "new" gun. Sure, if you count all those, there are tons of "new" guns.
I would agree that there are only so many T&E guns available and most channels cannot afford to buy every reviewed product without sponsorship of some kind.
However, the discussion of this point all goes back to:
What do people want to see on YT? What content will generate views, subscriptions, likes, comments, and revenue.
The point of my original thought was that:
This drives many YT'ers to the archives so to speak to demo and review older products or make the "this gun versus that gun" videos to piggyback on a previous installment.
People eventually get tired of the same old stuff. That is why content has to adapt and change to retain viewership. There may be new sku's to review, but do people want to watch that content? - Especially if they can't actually buy the gun right now. Sometimes, going to the archives is a good change of pace. Those who are differentiating themselves with original content stand out.... that is, until that content segment is overdone.