It's SHA-512 with a different IV (which is why you can't derive a compliant 512/256 from 512 directly) with the leftmost 256 bits taken as output. The rest of that stuff applies to all the SHA-2 hashes, I think.

None of this is security-relevant, including the IVs. You would have morally the same system if you just chopped 32 bytes off a SHA-512 hash.