I think perhaps you misread my previous comment. While everything you say is correct, it is not relevant to OP's case where he has already generated an English Electrum seed phrase and is simply looking at alternative ways to recover it. The differing checksum and version bit requirements are only relevant in generating the seed phrase as I said above, and are not relevant when it comes to turning an already generated seed phrase in to private keys and addresses.

You can take Ian Coleman's tool for example, tell it to ignore the BIP39 checksum check and swap the word "mnemonic" for the word "electrum", and it will recover standard English Electrum seed phrases just fine.