This is completely false. I never actually bothered testing this myself since I just trusted it was pretty simple, but when I was curious about Protean + Revelation Dance mechanics while typeless thanks to a bug reports post (http://www.smogon.com/forums/posts/7646904/), I found that Revelation Dance while type 1 was typeless, but a type 2 OR added type existed, just changed into type 2 if one existed, or the added type if not. The only way Revelation Dance will truly be typeless is if your current type is typeless alone.
I did those tests in USUM, so I thought maybe they updated it or something. Tested on Sun v1.2, same thing, so maybe they updated it in 1.1 or 1.2? Deleted the update and it's the same on v1.0 also.
Anyway, on to the Protean + Revelation Dance stuff:
Theoretically, Protean would have modified all the user's types into the single type it was changing to, but typeless was evidently not overwritten here. Did the same thing again without Revelation Dance, and got the same result:
Then I did the same thing without "changing" to a Flying type first, and got the same result:
Then I thought, what if your type 2 is typeless, does Protean still activate with no message when you use a type 1 attack? Yes:
As you saw earlier, Protean will not activate again if you keep using the same type attack again after having it activate with no message. As far as I can tell, it begins activating the first time because the game knows you currently have more than one type, but then fails to display the message about what type it's changing you to because it's the same type you already are. Burn Up, then Forest's Curse into typeless/Flying/Grass, then Protean does in fact show the message, presumably because you now have at least two types, one of which is not typeless.
tl;dr None of this is really useful information, just interesting mechanics.
Then, in this battle, https://replay.pokemonshowdown.com/gen7ou-689183458 turns 4 , 9, 12 and 15 are correct according to the original game(cart), right?? Just confirming.