So you're confused about ROOL #1? I don't blame you, this shit is complex. This rule sets up the majority of the premise of the DKU, so it's fucking loaded like a baked ass potato. Let me break it down for you into two parts: What and Why.
First of all, what is ROOL #1 saying? Well, there are four clauses here, each of which detailing an important point. Let's examine each of these bitches, one at a time, in what some people might call "FAR TOO MUCH DETAIL"...
I ain't afraid o' no blue-haired twat with a Super Soaker.
The first sentence begins, "The DKU begins with Donkey Kong Country", and means exactly that. We start off at DKC, and this means that games that came out before aren't DKU, including ALL the DK arcade appearances. The latter half of the sentence, "and specifically follows Rare's revised version of Donkey Kong featured therein" is a way of covering our ass for any DK arcade-inspired games that come out in modern day, because games featuring the arcade version of Donkey Kong rather than Rare's-tie-wearing-modern-day-hyphen-Kong would be DKU otherwise*. If this insanity is blowing your shit, you're not alone but just bear with me.
The second sentence begins, "it continues forward in time from this game's release". This means that games released before Donkey Kong Country can't be DKU. Other than excluding the DK arcade games, this non-retroactivity clause also prevents games such as Sabreman from becoming DKU, and by continuing forward in time, it also guarantees that a new DKU game can't make previous non-DKU games DKU. It continues, "and follows the characters from DKC and its sequels". This describes the first level of "DKU character", in that any and all characters debuting in DKC are significant and followed in every subsequent appearance they make.
In simpler terms, ROOL #1 means that Donkey Kong Country begins the cycle of "DKU character appearances", and nothing that comes before it is DKU. OBVIOUSLY. STICK WITH IT.
So now that you understand what ROOL #1 is trying to say, why the balls is it saying that? Well my plucky compatriot, there is in fact a rhyme and reason for this [there isn't ~ed]. We choose to begin the DKU at DKC rather than the previous Donkey Kong games because spiritually speaking, Donkey Kong Country is a reimagining of the series. Rare's reinvented version of Donkey Kong shared close ties to other Rare franchises Banjo and Conker, and so in an effort to segregate the franchises in a pro-Rare fan fashion, Donkey Kong Country is seen as the beginning of a new series. This is also supported by the fact that the Donkey Kong featured within Donkey Kong Country is not the same character as the one in Donkey Kong, but rather an adult version of Donkey Kong Jr. The fact that it stars a new character lends credence to the new beginning the series took, and the elements established within Donkey Kong Country are distinct, and have stuck with the series since in a way the previous arcade games haven't.
Donkey Kong, pictured raping the '90s Rare logo.
If you need another reason, let me explain the dilemma including Donkey Kong arcade would bring: If the DKU began with Donkey Kong arcade and the rest of THE ROOLS were left unedited, then the DKU would also be forced to encompass Mario's series. This is because Mario also debuted in the game alongside Donkey, and then spun off into his own franchise. If we had to cover every Mario game and every other spin-off associated with the series, then we would hardly be considered a Donkey Kong site. People might even think we're just WASTING OUR TIME writing on here! Haha!
Now, don't be fooled. We still consider these arcade games to be a part of the canon (in a way). However, in terms of our site coverage, we like to consider them as a mere backstory to the events of Donkey Kong Country, which really begins the franchise anew in a number of ways.
Hopefully this clears this up ROOL #1 for ya, and if not, don't worry! It's because you are in fact a moron, and definitely not because the system is overly complex and elaborate to the point of probable mental illness. DEFINITELY NOT.
*Some examples of this include modern day ports of the arcade games, as well as the Gameboy and Gameboy color releases of Game & Watch Gallery 1, 2, and 3, which featured arcade depictions of Donkey Kong and Donkey Kong Jr, but were not considered DKU. Game & Watch Gallery 4 on the GBA WAS ruled DKU however due to its title screen's very clear depiction of Rare's modern DKC Donkey Kong (even though our DK ISN'T IN THE ACTUAL "GAME" AT ALL, only aforementioned title screen; shaddap, WE LOVE STRICTLY OBEYING RULES).