John 12:33
John 12:3333He said this to indicate the kind of death He was going to die.
is not a verse JWs cite for any distinctive doctrine. It functions as a narrator's aside explaining what Jesus meant by being "lifted up." JWs read it the way most readers do — John is signalling the manner of the crucifixion. Where it surfaces in apologetic conversation is incidental: it shows up when someone is asking why the NWT renders estin as "means" at the Last Supper, because contains the word for "signify" that Jesus did not use.
The verse is a quiet but decisive piece of evidence for the Eucharist translation question. John uses the participle of sēmainō — "signifying what kind of death he was about to die." This is the ordinary Greek verb for "to signify" or "to indicate." When a New Testament writer wants to flag a symbolic meaning, the vocabulary is available and gets used. The contrast with the Last Supper passages is exact: at Matt 26:26, , , and 1 Cor 11:24 Jesus uses the bare copula estin, not sēmainō. If he had wanted the bread and wine to be plainly symbolic, shows the word he could have used.