So this is actually the second remaster of the game. The first one was released several years ago, and I believe it was mostly just a pretty typical HD remaster. This one was released a couple weeks ago and further updates the graphics and audio, while also adding several new features along with a new sidequest that connects the story of this game with the sequel.
What LRG is offering here is the remaster that was released a couple weeks ago, but in physical format, as it was digital-only and didn't get a retail physical release. Basically for anyone who wants a physical copy of the game, either to collect or for preservation. (Though not so much preservation for the PC edition, since it'll still be bound by Ubisoft Connect's DRM.) Or in the case of the Collector's Edition, anyone who wants the trinkets and things that it comes with.
No problem at all! And yeah, that's pretty much it! There are a handful of companies that are doing this. Some better than others. LRG is unquestionably the largest, which is why they make up over half of the posts that I make here.
Originally, these limited print companies largely focused on indie games. Basically, they were a way for independent devs to get physical releases for their games that wouldn't have gotten one otherwise. Indie games still make up the majority of these limited prints, but as things have continually shifted towards digital distribution, some big companies (like Sega, Konami, and in this case, Ubisoft) have contracted LRG for their print runs. I'm guessing it's for games where they feel that there's enough of a demand for a physical release, but not enough to mass-produce them and take on the risk themselves.
Personally, I buy them for preservation. I don't like DRM and I like having physical copies of my games. So I've only ever bought standard editions, myself. And despite how many I post about in this community, I actually only buy a few per year! Just the ones I care about most. The last one I bought was about 4 months ago.