I recently got a chance to handle some of the new Primbles and the newest incarnation of black box Winchesters. They are, without a doubt made by the same guy. Who's that guy? Ugh...
See the Stockman in the OP with the corset shield? Look at that nail nick. It was cut into the blade by an abrasive wheel. You see the same nail nick in the new Winchesters too. It's not always straight, aligned with the blade spine, or of consistent depth. The adjacent blades on these knives can be oversprung like crazy. Finish on the blades can be decent, it can be awful. The photos in the OP are catalog photos. I'd bet you that if you had that knife in hand you'd swear the blade was finished on a wire wheel.
As for the 'who': Bluegrass is one of the most highly guarded secrets on earth. My theory (which might be complete doo-doo) is that they manufactured knives in the past, assembled knives for many years, and nowadays they contract their knives.
The contractor... Bear and Sons. Bear is capable of making a fine knife, and they made lots of them. I buy the nice ones every chance I get. They also make a lot of cheap and dirty knives. Nothing wrong with them, but you're not going to mistake one of them for a forty-year-old Queen-made Winchester. They resemble the last days of Schrade. Poor blade finish, scale materials that aren't quite right, weird blade combinations. Look at the overall shape of the handle and blades. They're not quite right.
Now for the Ugh... During the early 2020s, you remember what was going on then, I bought some Primbles online. They were dead ringers for these knives. But they had China etched on the reverse tang and a USA tang stamp on the front. If they were sold as $20 knives that would be one thing, but they weren't. Not impressed.
In my opinion they're not a bad knife, they are overpriced, and are of highly variable quality, and I'm dubious of the USA manufacture claim. If you can't inspect them before buying, at least buy from a dealer who has a good return policy.