Yes, really, Wil. All those rules reflected underlying realities in simplifed terms. Traveller even more so than the rest of your list.
(Well, I never saw a copy of the T&T rules, but I would be most surprised if it wasn't the case with T&T too).
Hans
WRONG.
Not a one of them had a default setting nor "history" to reflect. The settings came later. The rules defined the default setting for D&D and T&T, NOT THE OTHER WAY AROUND.
Including where Gygax, in D&D, states there is no particular "reality" being emulated by D&D. (Volume 1, page 4.)
These rules are as complete as possible within the limitations imposed by the space of three booklets. That is, they cover the major aspects of fantasy campaigns but still remain flexible. As with any other set of miniatures rules they are guidelines to follow in designing your own fantastic-medieval campaign. They provide the framework around which you will build a game of simplicity or tremendous complexity — your time and imagination are about the only limiting factors, and the fact that you have purchased these rules tends to indicate that there is no lack of imagination — the fascination of the game will tend to make participants find more and more time. We advise, however, that a campaign be begun slowly, following the steps outlined herein, so as to avoid becoming too bogged down with unfamiliar details at first.
T&T tells the GM to develop his own game world, and to date, still strictly avoids putting "setting" into the core. Any setting present arises from the mechanical inclusions. Deluxe will actually change this - the 8th edition will be the first with a setting explicitly included, and at nearly 40 years from its first publication (1975).
There's no underlying reality - only what the GM gets into his skull and what the rules create. Which is why every original edition D&D campaign was a fundamentally unique setting and experience - the rules were vague, and didn't create a strong setting, and there was NO setting fluff.
CT Bk1-3 was much the same. It was released as pure rules, with just enough text to make sense of the Careers. We know there's an imperium, with nobles. We know each world has its own laws. In the exact same way we know that high level fighters have followers in D&D - because it's in the mechanics.
99% of the feel of Traveller isn't the OTU. It's the tropes which are built into the traveller rules (and many of which, GT gets wrong, By the way).
Until Mega was released, Traveller's core rules had more implied than explicit setting, and unless you bought the supplements, your ability to run the OTU was negligible, because it wasn't in the rulebooks. Hence, most people's games varied widely.
That the rules can be measured against our reality doesn't mean that our reality is the same as the game emulating an underlying reality - the game is a reality of its own - the mechanics
defined the setting for a great many players.
I'll also take Arneson's word over yours - there was no singular "reality" behind his rules, which are the core of old school D&D. Gygax and Arneson both chose multiple, sometimes contradictory settings to inform their game designs (both jointly and separately), and it's utterly presumptuous to claim they tried to emulate some singular reality when they have both repeatedly and explicitly stated that they hadn't, and that the rules needed to be tweaked if one wanted to emulate some particular reality.
Hans, you're blinded both by your adherence to universal systems and your insistence upon Traveller having "some common reality behind it poorly reflected by the rules." You have never accepted that the CT rules were written before the setting, even tho' it's explicit that Marc came up with the rules after watching Star Wars, but informed by older sci-fi in mishmash.
If there is a common reality behind Classic Traveller, is sure as hell isn't the OTU... because the OTU almost needs a setting book of its own. Even MT was mechanically CT hybridized with Striker, not a serious attempt to emulate the setting.