One of the problems with Traveller, both in terms of background and rules, is the perceived need to codify everything precisely...
You know, I never saw this when I started playing way back, only after unvetted random UWPs were published as sourcebooks and after the swing in RPGs from "Ref creates game and adventures, players create characters, have fun." to the "Ref buys modules, players read rules, win the game."
UWPs are too generalized in my opinion to be taken as a hard exact description. And any attempt to make them more so is probably pointless as you noted with excellent points. Maybe worse, more scientifically accurate (meaning for what we know at the moment, likely to be out of date tommorrow), attempts is probably as pointless.
I don't think the UWP was ever meant to be anything other than an imagination trigger. It was never meant to be the imagination killer so many now seem to treat it as, feeling stuck with the results no matter how nonsensical.
The real problem is when something so obviously meant to be interpreted is used "as written" without interpretation and made canon (yes, I used The Word*). As much as you and others would like to fix it where it's been done wrong that's a harder thing than getting it right the first time. And getting it right the first time would have been a lot of work.
* Canon is not a curse, at least it should not be, it should be helpful but it needs to be properly vetted and followed by publishers to be so.
In short I agree with you that (at least some parts of) Traveller "rules" (all RPGs really) should be guides, loose, and subjected to interpretation before use. The thing is I've always felt they were just that originally and it's only later usage and publication that have gotten away from that. And I see that as largely market driven; refs and players now (and for years if not decades) seem to demand and/or expect it. Wanting to be able to jump right into the game and play. Not "waste" a bunch of time setting up and interpreting the rules with an attitude of "If I wanted to write the whole game myself... "