I don't buy that theory. The more they release with the expansions, the more I'm convinced that Destiny's story is exactly how it was originally planned to be--maybe not how it's presented, but I suspect that much of the narrative has remained as it was envisioned to be.

I suspect that is not the case. Presentation and delivery IS everything. Look at that super soldier with his blue AI friend saving humanity, certainly no the most original story, but man, did it deliver!

Presentation and delivery is huge, without doubt. My contention lies in the theory that the story and lore behind Destiny was gutted and then reworked only a short time before release. The creator of the video posted in the OP took the large bulk of his narrative from the grimoire cards and from information taken from the game itself (e.g., in game dialogue, cut scenes, etc., trailers). He also has a couple other videos on his YouTube channel titled "10 Things You Don't Know About Destiny" (parts 1 & 2), again using information taken from the grimoire cards and the game itself. As I said in my first comment the more they release with the expansions (and unlike @NeckPUNCHattack, I will refer to them as expanions, because they're definitely not DLC, with much of that content already being in the game whether in whole or in part via placeholders), the more I'm convinced that the story is as it should be. All the information found in the game and in the grimoire cards is way to extensive for me to believe that it's all patch work and a last ditch effort to save a sinking ship after Joe Staten left Bungie. I think it's also safe to assume that the rights to whatever work Joe Staten did for Destiny would belong to Bungie and and even if the split wasn't as amicable as the official story portrays, it makes little sense to me that Bungie would need to worry about coming up with something to replace the work he put into it just because he left. With a ten year plan for the IP there's plenty of time to flesh out the story through coming expansions and sequels. I don't think it's too much of a stretch to think that much of what's been claimed to have been changed still might be part of the story that's to come later (i.e., the stuff about the Queen's brother, the true nature of the Traveler, etc.).

You don't buy that theory?? You clearly haven't read up on any of Bungie's last minute issues & changes before the game released. The grimoire cards were actually written 7 months before destiny was released. Joe (the lead writer) left Bungie approx a year before destiny came out & bungie had to pick up the pieces & salvage the mess of a story that they had on their hands. If you do a little digging, you'll find out that the grimoire lore was in a basic form from the notes Joe left behind, but Bungie hired a writer solely for the purpose of writing the grimoire cards because they were out of time and couldn't re-create cutscenes explaining the story/lore, so the whole grimoire concept was deemed the quickest/best way to tell the back story without delaying the game. This isn't a theory, it's a fact. If you do a little research and go back 8-9 months before Sept.9, 2014 and search the job postings Bungie created, you'd easily find that a "writing position for the series lore" was posted, and the writer who got the grimoire writing job came on board and finished all of the pre-game grimoire lore 7 months before the retail game came out. New grimoire cards are created from this point on to continue their "idea" of story telling, but it literally was a last minute patch job to salvage the story and stick to their deadline. And each DLC (don't call them expansions - they barely have enough recycled content to even be called dlc) so far has been an attempt to flesh out their universe, but as of this point, they keep messing it up (and they even acknowledge this in interviews) & don't expand on much of anything. When the 1st comet expansion hits, we'll see a more fleshed out story, but until then, we're getting recycled environments & content that was in the game as early as the Alpha. The only difference is that Eris was created as a new asset after the game was released, everything else was reworked & salvaged from the original storyline that was scrapped after Joe S. left. Don't believe that? you can even hear it direct from DeeJ when he constantly comments about how we "shouldn't buy into leaked content since all those assets are placeholders". They don't come out and say it, but if you use your brain, you can see whenever leaked content surfaces, he chooses his words carefully, and it's usually repeating the phrases "placeholders", "story will most likely change", and "don't believe everything you see that was leaked". They can't admit it, but this game was dismantled and reworked less than a year before release & the grimoire lore is one of the MANY things used to patch the non-existent story. So no, it wasn't the original "envisioned" idea for the game, but it's what we got and what we have to deal with moving forward.

Negative, look at the information on the web including the tweets by the guy who wrote the grimoire. It was shortly after there lead story guy Joseph Statten quit and they didn't want to pay him royalties on everything he created.