How do you perform sha256 by hand? That's not called being genius but rather stupid, because you could just use a script to do that for you. Also there is no need to generate seeds manually, just use a standard and secure wallet to do all of that. Manipulating things like that is bound for disaster.
Hello.
Nothing has been manipulated here. This is how the BIP 39 seed phrase is derived from a 256 bit random number.
Thanks for your input - the subject was "understanding BIP 39 as a layperson" so yes, it may or may not be important to any given individual, not sure, if BIP 39 will remain as an important protocol in bitcoin, or if bitcoin is important to the world in general.