From what I've seen at the Amsterdam Meets over the years, is that that can be three stages in a design. It often seems to start with a Concept Model that will be shown at various shows to gauge response and help decide whether to produce that design or not. This stage can last a few years for some designs. It has always been 'verboten'
to photograph and publish a Concept Model online. In the case of custom collaborations, a concept model would often be a custom made knife by the custom maker involved.
After that, a design appears to become a Production Prototype, where the original design is translated into a production version. This stage appears to take between a year and two years. This is the moment when we -in the past- could shoot a photo and share it online, in close co-operation with Spyderco. In recent years, the production prototype appeared ever closer to the actual production model. In the past, I think I saw more tweaks etc.. to the production version versus the production prototype.
The last phase is the actual production knife. And this can be refined and changed based on customer feedback. CQI etc...
Now, this process is certainly not set in stone. A design can sometimes be too complicated to produce, and technology has to 'catch up' for production to become possible. I tend to think of the Tusk as an example of this, I recall seeing this concept model at one of the early Amsterdam Meets. Other times, it appears to be a matter of planning a new model in between many other ongoing production processes. But the above, is what I picked up from attending all of the Amsterdam Meets. The market can change it mind too ofcourse. It could very well be possible that the market didn't like the Native Chief design 20 years ago, when the Native itself was primarily known as an FRN handled design. Now that the market warmed up to a G10 Native, a larger Native Chief might have been more welcome. Again, this is just supposition on my part.