Yea I am with you on this. It's kind of ridiculous that they can't just come out and show us some of the final build. I don't think I have ever seen a game developer have so many builds of a game and not show off the final one this close to release before. This game has had the strangest development structure I have ever seen.
This is not really correct. Developers create new builds of the game many times when working on a project, even up until the release the game will still be undergoing many builds, especially towards the end because they will be doing a lot of play testing and a lot of bug fixes and optimizations. To say that they should have a "final" build by now comes from ignorance about development. That is not meant to be an insult to you by any means, it just means that you are not aware of how these things operate.
What a build is referring to is when you compile the code for your project and it creates a single executable that can be run, that's referred to as a "build". Let's say you just ran the most current build on the stable branch of the game and suddenly you noticed that whenever you used this one ability in the game that you're getting this huge performance hit over time. So, you open up some profiling tools and realize there's a memory leak happening, so you start debugging the build and you realizing that the ability was made wrong and none of the memory that get allocated from using this ability was ever freed and so every time you use the ability it just eats more and more memory. So, you fix the code and you create a new build for the game, and now you fixed the bug.
This scenario is just simplified to make it easier to understand, in reality this sort of thing likely wouldn't happen specifically for reasons I won't get into due to the complexity of the explanation, but I think you can understand how this workflow breaks down. It's very common to create thousands of builds of a game, especially one this large, and isn't at all uncommon in game development.
The reason you often see a lot of different older builds being shown off is because they are more stable, I made a reference to something I called "stable branch", what I was alluding to was a branch from the repository for the game's engine. A repository (repo for short) in development is version control software, commonly used versions are GIT and SVN for example. The way you use a repo in development is by "committing" changes from your codebase to this repo which stores only the changes in the files to cut down on how much space it takes up.
For example, if you refactored a huge chunk of the engine, but it ultimately was only changing a few names of specific words or a couple line changes here and there across 1,000+ files, instead of saving a copy of 1,000+ files somewhere, you only save the exact changes additions or removal of lines etc.
Commonly, when working on experimental changes or big changes to the engine which might break other parts without further testing, you create something called a "branch". If you wanted to make large changes to let's say the AI, you would create a branch for this so that you could commit your changes and have them saved, then later on when they become more stable, you can merge them into the main branch so that it can be apart of the main project.
What this means is for many presentations and public appearances, you will see older more stable builds being used as they are less likely to crash and are known to be stable, but may not have all the new features that are currently being worked on. It's very possible that you will see a build of the game that is actually somewhat behind what is being worked on in development that is mostly stable but has yet to be merged.
The point of me explaining version control software and technical things like this is to show you and others who might be unaware that having many builds in a project is a part of development, in fact, the less builds you have of a game, the more likely it's going to be a failure as that means you are not using version control software properly, or you are not doing much development on the game at all.
I hope that I made sense with my technical explanations and that you might understand a little more. The big difference between FFXV showing off their development more than other games has to do with the game's origins when we would go entire years without even reading about the game let alone seeing it. Ever since the rebranding, there has been a major shift within SE to show this game as much as possible and to be very upfront about the development. Tabata has done a lot for this game, and even has radically changed the way many current Japanese business structures operate in order to bring new life into BD2 to achieve a more productive work environment, and showing off their technology so openly and even admitting things like frame drops and performance is a testament to their passion for this game and to always be upfront and honest.
For me, I really love seeing the behind the scenes look at video games, it's something I miss from back in the day from things like PlayStation Underground where they would show games in development or a look at a game dev studio where you can see all their software on screen and learn about how these games achieved their technical accomplishments.
I'm going to stop rambling now...