I don’t see why other Pokémon scaling or not scaling to the Creation Trio is relevant to this thread. Darkrai and Cresselia are only mentioned in the OP because they’re already accepted to be scaling to the Creation Trio. The thread isn’t trying to change any scaling chains, only the cosmology.
This is precisely why I didn't want this thread to be changed into a scaling discussion and take away from the actual topic here. Especially when a lot of this has been accepted for ages and is only just now being questioned.
But if it needs to be discussed here
Rewatching the Darkrai movie, there honestly aren’t any direct statements saying Darkrai is on the same level as the Creation Trio, nor is his level some central point of the plot or anything like that. Darkrai and the two dragons just exchange a few blows and are shown to be capable of dodging each other’s attacks.
Darkrai’s case & and the Hoopa debacle are 2 vastly different cases. But more importantly, Darkrai’s battle with Dialga & Palkia being reduced to just “exchanging a few attacks” is just outright not true.
Darkrai’s contention with Dialga & Palkia is plot essential, as he’s the only Pokemon in the movie (his debut movie where he’s a central character, also) strong enough to fend against them & keep Alamos Town from being instantly vaporized. His fight with them also isn’t just a “one off” thing. Theres a consistent line of feats
throughout the movie that demonstrate Darkrai blatantly holding his own against both of them at once.
Darkrai sensing Palkia being an extreme threat, him briefly battling Palkia as an equal, once Dialga joins in Darkrai is blocking attacks from the 2 of them, directly taking several of their attacks head on and continuing to stand against them. The movie even makes it a point for Darkrai to stop their collusion of Roar of Time & Spacial Rend, which would’ve destroyed the dimensional rift, by absorbing them into himself. In order to buy Ash and the others time to play Oracion and stop the whole conflict. Darkrai protecting Alamos Town & the dimensional rift is an important point of the plot & it’s a consistent thing we see.
Not to mention, it’s not just in the anime where Darkrai’s shown world-ending feats & being comparable to Dialga & Palkia. Darkrai has his own Tier 2 feat from Pokepark of merging universes. And in Mystery Dungeon, Darkrai is outright the antagonist & is the reason Primal Dialga happened in the first place. It has also taken serious attacks from bloodlusted Palkia & whatnot and can still live to tell about it afterwards.
If that’s enough to scale, then the Pokémon in the Hoopa movie should scale as well.
Hoopa and the Clash of Ages, however, is just pulling legendaries from different gens all into one place, where these legendaries have lore & scaling that,
as of right now, have absolutely 0 business in being anywhere close to the same level as the Creation Trio. With a plot about legendaries having a battle Royale, of course there's going to be expected showings of these legendaries battling ones they very much shouldn't be. Thats why we can claim PIS. You have to take this into account when thinking about these legendaries lores and their respective places within it beforehand.
And keep in mind too, unlike with Darkrai, this is the ONLY time out of any Pokemon media that they have any kind of interaction involving the Creation Trio here. Even if Clash of Ages was to be tried taken seriously in powerscaling, this is
one instance vs a consistent number of other ones where these legendaries portrayals are vastly inferior to the CT.
Hell, even if you take the CT out of the equation, the feats are still outliers. Primal Groudon & Kyogre are now comparable to White/Black Kyurem? The same Kyurem who's > Genesect, who's = Mega Mewtwo, who's inferior to Mega Rayquaza? The latter who's 110% superior to the Primals?