because Electrum seed (as it was mentioned are not BIP39) are generated in a way that they will not be a valid BIP39 mnemonic and should be rejected by wallets validating such seed phrases!
why would they want to avoid being complaint with a standard. That doesn't make any sense. did they just do a "roll your own" kind of thing and think it's better for some reason? almost every other wallet is compliant they aren't. go figure.