When I was a Lutheran, I don’t remember the word " Consubstantiation" being used. But it came to about the same thing. As the pastor–and again a later pastor, when I was older–explained, “It’s both. It certainly has become the body and blood of Jesus, but you can see and feel that it is still a wafer and wine. It is both at once.”
Also, Lutherans do use wine, not grape juice. There seems to be some misunderstanding about that, too.
<<the bread and the wine and the Body and the Blood are united in some way that, more or less, creates some new, third substance>> No, that doesn’t sound like anything I heard as a Lutheran. I guess you could say we were tap dancing around the edges of that, but there was never a “third substance” mentioned. And neither was the word “consubstantiation” mentioned.
Both of my old pastors have passed on, so I can’t look them up and ask them for clarification here.
One thing you don’t hear much of among Lutherans is the concept of other religions getting “duped.” We note that nobody has come back from the other side to tell us how they fare, or to tell us that Christ personally told them this or that, so we like to think that some of it is just unknowable in this world.