Yeah, that's pretty much it.I see what you're getting at.
It's basically a case of "room for homebrew" where the rules enable almost anything and the setting is optional ... rather than the setting being the primary focus with the rules confined to operating within that setting almost exclusively.
It's one of the hazards of game design, knowing that there have to be limits (somewhere) ... whether that be the edge of a map, the limitations of tech levels (and everything those imply in a sci-fi genre) or even the ease of acquisition/loss of "loot" (see: Monty Haul campaign).
Due to the space limitations of LBB 1-3, there simply wasn't room to detail an official game setting in tremendous detail (like you can do now with online tools such as Campfire Blaze that can keep track of EVERYTHING in a setting for you, as a writer). That very lack of room to "definitively define" much of an official setting yielded a kind of No Man's Sky version of Traveller in the early days. Even LBB A1 The Kinunir was limited to only the Regina subsector for a map. Then LBB S3 Spinward Marches came along and we got to see the sector that the Regina subsector was set in ... and after that, the rest is history ... all the way up to online tools such as Traveller Map and the Traveller Wiki sites.
There's a very different ... sense ... of possibilities when you start small but have room to explore and grow and build using that small start as a foundation. A kind of small fish in a small pond that leads to a bigger lake of unexplored possibilities ... rather than being a grain of sand on a beach made up of seemingly countless sand grains. In a very real sense, what amounts to "archipelago campaigns" in which there are known (small) clusters to navigate between and within tend to offer the richest possible settings because each region is "small enough" for a Referee to manage (and keep track of) while also leaving "room" for the archipelago to grow and expand outwards somewhat organically in a spirit of exploration into aster incognita.
When one of my high school to college era groups did Champions the VIPER supervillain group was an optional bad guy outfit that was offered by the basic rule book. They were a stock bad guy super villain outfit that the players could use in a pinch in lieu of making something themselves or trying to recreate somethiing like DC's Legion of Supervillains or similar supervillain groups. It wasn't "canon". It was there as a tool should you need it.
And to me that's what original flavor Traveller was all about. Even when FASA and Judge's Guild were publishing their addons, there was still a Proto-Traveller feel to the game. And that's how the rules were written. When Hunter was still alive and tabled an offer to write for his T20 ... I was trying to finish my degree at the time, but more importantly, author wise, I had a hard time wrapping my brain around the OTU. I mean I knew it backwards and forwards like a lot of people who post here, but my early experiences with the early "Non-Setting" version of the game is what sticks with me.
I can't say I dislike the OTU for the game, but regardless of why more background material wasn't put into the first basic LBBs, again just my perspective here, I prefer material that doesn't reference the OTU. So the few adventures that I have written were done in that vein.
To me the OTU just feels like it pigeon holes and excludes a lot of possibilities by being the OTU by law as opposed to the OTU as an option should you need it or elements of it. And like I say back in the 60s and 70s there was really new and unique scifi art that was more colorful and imaginative than the pulp book covers from the 50s. So much that Stewart Cowley put them into his Terran Trade Authority series, and Traveller, in my not so humble opinion, rode off of that vibe sparked by Lucas's Star Wars.
So ... reinventing the game, to me, is not dependent on shifting emphasis on the temporal or historic era for the OTU, but getting back to the original basics of being a GURPS like RPG with an optional background for players. That's the game I know, that's the game I grew up with, that's the game I wanted to write for, but other than shooting my mouth off here, I've essentially put it on the shelf and will never go back to it in any form. Such is life.