-snip-
You are confusing the process of going from entropy to a seed phrase (which is what you are talking about), and the process of going from a seed phrase to a private key (what OP is talking about).
As you've quoted, you take the SHA256 hash of your entropy to generate a checksum, which is appended to the entropy before the resulting number is used to generate a seed phrase. However, once you have the seed phrase as in OP's case, you don't use SHA256 in the generation of private keys, but rather HMAC-SHA512. Using SHA256 on a seed phrase is essentially creating a brain wallet, as nc50lc has said above.
Yes this is the very first step of the process and as you can see you have to pass through it to compute your seed from your entropy source. I think this is the origin of the mistake of zorenskye1212, he confused the process of getting his seed from an entropy source and the process of getting an address from his seed.