You have got different address cuz starting from the version 2.0 Electrum
derives keys and addresses from a hash of the UTF8 normalized seed phrase with no dependency on a fixed wordlist.
that isn't exactly the same as BIP39 scheme.
That's not accurate. Both address he gave are generate from the above BIP39 seed phrase at different derivation paths, as I showed in my last post.
Go to
https://iancoleman.io/bip39/Paste in the above seed phrase to the "BIP39 Mnemonic" field
Scroll down to "Derivation Path" and select "BIP32"
Under "Client" select "Custom derivation path"
Under "BIP32 Derivation Path" paste m/44'/0'/1'/1, scroll down, and the first address is 1Z1EM...
Under "BIP32 Derivation Path" paste m/44'/0'/1'/1'/0, scroll down, and the first address is 1NAxs...
Although Electrum by default doesn't use BIP39 seed phrases, when importing a seed phrase to Electrum you can click "Options" and select "BIP39 seed", as blue Snow must have done, otherwise he wouldn't have obtained the 1NAxs... address.
OK. bare BIP39 is still supported but will be deprecated in the future version, at least that is what 3.3.8 client says right now. Anyway the generation scheme of the current and all future Electrum is different from bare BIP39.