It's possible that this product was intended to be based on M2, but support for multi die M1 was built in from the start as a hedge to avoid the kind of stagnat

It's possible that this product was intended to be based on M2, but support for multi die M1 was built in from the start as a hedge to avoid the kind of stagnation Intel has seen, where a node delay means they can't ship products. I'm not saying that's what happened, but it's a charitable reading of the original post.