from tenelli- "Passaggio exists as a a sensation for every living voice and often as a register(transitive) not just a sensation. In appoggio technique there are no real registers(Sensations only) because appoggio singers are using chiaro-scuro all the way from the bottom to the top, they just support it and not replace it into a new register. I can see that Mr.Rocksell Blake is from Placement school of thinking, or even singing. I suggest to read Lily Lehmann, Caruso, Gigli that deny this Placement nonsense"
i dont know about the specifics, but what i think he's saying is there is a passagio and register change but with proper technique its smoothed out and made to not look like there is one. and isn't that what part of vocal training is about, navigating the passagio, whereas this blake guy denies it exists just because he can sing it smoothly because of his good technique, whereas beginners pretty much cant. or at least thats what i gather from things i read about vocal training.