they've only ended production of 20 nm B-die and have started production of 10 nm B-die
That's really NOT the same thing. And my understanding is that these so-called "a-die, b-die, etc.", are effectively revisions
for each different process node.
So yes, the dies that are called "B-die" among enthusiast circles, according to YOUR OWN WORDS, are cancelled.
The fact that they have a new die,
also labelled "b-die" by the mfg, but on a different process, is largely irrelevant. Different process, different product, we'll see how the enthusiast crowd reacts to them.
That's almost like saying, "Hey Corsair Vengeance (DDR3) is cancelled, but you can still get Corsair Vengeance (DDR4)". That's basically what you're saying, by way of analogy.
(*Nota Bene: AFAIK, Corsair Vengeance in both DDR3 and DDR4 are still being made, that was just a hypothetical analogy example.)