[cyberax]

You don't need them to be entangled to act as a boson.

A Cooper pair is a composite object, and you absolutely need to consider the atomic lattice of the superconductor.

So you end up with your electron being entangled with all the surrounding atoms in the lattice. And all other electrons.

[drdeca]

Ah, so it isn't so much that they don't need to be entangled, so much as, describing them as entangled isn't a good way to frame it, because all the electrons (and the rest of the material) will be all entangled with each-other, so, it isn't a distinguishing feature, and misleading to focus on the two in the pair being entangled?

[cyberax]

Yes, pretty much.