I'm not sure which rulebook you're saying has an "implicit" twist rule.There's a one sentence rule that says "in this case, make something up." This rule is explicit in one rulebook and implicit in another. The rule itself is vague- "do something" isn't very specific. But I think I see your point here. However, I find it very difficult to understand how not being explicitly told that the GM needs to do something in a particular instance, especially in the frame of NPC reactions, is a failure of campaign design.
There is no implicit rule in RM that, if a PC fails (say) a Perception check, the proper narration of a consequence is that their enemy shows up. In fact, that would be considered pretty outrageous, because it breaks the nexus between then at-the-table process of resolution and the in-the-fiction process of the character looking around.
I also think that there is no such implicit rule in classic D&D, nor in 3E D&D, and I've never seen it suggested that it was an implicit rule in 5e D&D. It is a rule, implicitly stated, in 4e D&D - the example which reveals it but doesn't expressly state it is the skill challenge example in the Rules Compendium (where a failed knowledge check, in relation to an abandoned building, has the consequence that an enemy NPC turns up).
I posted this back in 2012:
This example, and ones like, it - which is an example of the "twist" approach found in Torchbearer, although back then I was referring to other RPGs that use similar approaches like HeroWars and Burning Wheel - produce responses like "Why does my failed attempt at diplomacy cause it to rain?"When it comes to out-of-combat resolution, the main requirement is to explain to GMs how to resolve the failed checks that will inevitably follow upon players making checks in which their PCs have poor bonuses. Burning Wheel does an excellent job of this. D&D, to date, has done a terrible job. Judging from posts I read around here, the default narration for the dwarf fighter attempting and failing the Diplomacy check is "You open your mouth and spray your spit over the mayor - sucks to dump CHA, I guess!" - and then people complain that their players won't use anything but their biggest numbers!
If the fighter fails the Diplomacy check, then there are any number of ways of narrating that failure without making the PC look like a fool - from "The mayor listens briefly, but then excuses herself to go off to the next meeting" to "Of course the mayor would love to help you, but she swore an oath to her late brother that she would never do XYZ" to "As you begin your address, rain starts to fall, and the mayor's entourage usher her back into the city hall before you can get your point across".
And still do. For instance, you can see references to "Schroedinger's encounter" or "Schroedinger' secret door" very often in posts made in recent threads on these boards.