Maybe not Nintendo but of VV? A western studio? They’d be privy.
This rumor has been discussed in the Donkey Kong OT a lot.
Yeah, what was (allegedly) leaked is from VV.
However, there are some parts which are IMHO too detailed
Retro's Twitter account cryptically tweeted a week before E3 2015, but rumors that Nintendo was reportedly unsatisfied with it and it failing to find a direction meant it never saw the light of day. The meaning behind "Can you dig it?" was thus never uncovered.
We know nothing about the game from Retro, the super-secret developer studio,
but we know it was going to be on E3 2015 and Nintendo pulled it out at the eleventh hour. Logically, the source should also know a bit about the game.
We know Nintendo did put the kibosh on Retro using K. Rool as a new secret final boss in the Switch port of Tropical Freeze, partially because they wanted to preserve the impact of him being in Smash.
Again, nobody knows anything about Retro, and nobody knows anything about Smash characters.
But we 100% know that Retro wanted K. Rool in the Switch port of Tropical Freeze, and that Nintendo wanted the character in Smash first. Assuming this is true, they could have released TF after Smash and banking on the character's popularity. But in order to assume it is true, we have to assume that we have a source with a deep knowledge not only of Retro (and at this point, shouldn't Retro's game has been laked as well?), but of the Japanese side of Nintendo as well. It's too much.
I believe the overal story is plausible, but these accidental details are too specific and cast a shadow on the whole leak. These details were also never mentioned by the only two reputable Retro leakers we have (Belmont and Emily) -- though, to be fair, they never talked about these topics specifically.
On this very message board, we have two user who I assume are both in good faith with conflicting opinion.
@Professor Chops has reported the same story one year ago (but IIRC believe he didn't confirm the K Rool detail).
@PikminSnezkov, who leaked TTYD remake, claimed the story has been fabricated, but he believes in a DK game by EPD.