Yes, you are correct. I feel that D&D, in particular, delivers these through received wisdom rather than actually putting it out there, though, so if you're exposure is primarily through D&D or games that share it's received wisdom approach on how to play it, this probably doesn't occur to you (it didn't to me, I took a few tries before I saw it). Playing a few games that make this explicitly part of the game, that provide clear direction, principle, and techniques on how to run it, can be illuminating.
There are also games that are contradictory in the principles that they imply. Here's an example from Classic Traveller (1977). The first, third and fourth quoted paragraphs are from Book 3, pp 44, 19 and 8; the second is from Book 2, p 36 (I've presented the paragraphs in this sequence for expository purposes):
Above all, the referee and players work together. Care must be taken that the referee does not simply lay fortune in the path of the players, but the situation is not primarily an adversary relationship. The referee simply administers rules in situations where the players themselves have an incomplete understanding of the universe. The results should reflect a consistent reality.
When a ship enters a star system, there is a chance that any one of a variety of ships will be encountered. The ship encounter table is used to determine the specific type of vessel which is met. This result may, and should, be superseded by the referee in specific situations, especially if a newly entered system is in military or civil turmoil, or involves other circumstances.
Some random encounters are mandated by the referee. For example, a band may encounter a guard patrol at a building while in the course of visiting (or burglarizing) it. There referee is always free to impose encounters to further the cause of the adventure being played; in many cases, he actually has a responsibility to do so.
[T]he referee should always feel free to impose worlds which have been deliberately (rather than randomly) generated. Often such planets will be devised specifically to reward or torment players.
The first paragraph suggests a hard purist-for-system simulationist agenda with neutral refereeing as the goal; and for many years this is how I read Traveller. It is reinforced by the design of the early published scenarios like Annic Nova and Shadows and Mission to Mithril and Across the Bright Face.
The second paragraph, and the second sentence of the third paragraph, can be read consistently with this, as suggesting logical extrapolation, by the referee, of the consistent reality. But the third sentence of the third paragraph, and particularly the clause after the semi-colon, runs in a completely different direction. It suggests something closer to PbtA or scene-framed play. And the fourth paragraph doesn't seem at all consistent with neutral refereeing of a consistent reality! (And if the GM is deliberately "tormenting" the players, how is the relationship
not adversarial to some significant degree?)
I don't think there's any way of reconciling all the rules text that I've quoted. The second paragraph, and the second sentence of the third paragraph, can be read differently from what I suggested just above, and consistently with the rest of the third paragraph and the fourth paragraph: instead of logical extrapolation, the GM is stipulating these encounters because they're interesting! But that requires hanging the first paragraph out to dry. The referee is no longer simply administering rules; s/he is making stuff up to "reward or torment" - or more generally, to engage - the players.
(I put to one side a third possible way of making sense of Traveller - as like classic dungeon-crawling only space-crawling instead. The game itself recognises, implicitly in some places and explicitly in others, that the scope of the fiction is to expansive to permit generation all in advance. The referee is going to have to make stuff up in the course of play. I don't know Stars Without Number well enough to know how it squares this circle; but Classic Traveller just doesn't.)
Since I've discovered this second way of approaching Traveller - through a combination of rereading the text and bringing some other RPG skills and knowledge to bear - I've found it a much more compelling RPG! It's almost a proto-PbtA system. But to do that I had to just set aside some of the contradictory statements of principle.