- BIP39 passphrase does not encrypt, it is an extension of the seed phrase. All BIP39 seed phrases have an empty ("") passphrase by default, and you can choose to extend that.
- Wallet passwords are used to encrypt wallet files (such as Electrum's password), but as I already said, that's going off-topic.
I had already understood this and always knew it.
The seed phrase is encrypted in the keystore of the aforementioned wallets with the password chosen by the user. See that I used the term 'password' for Keystore encryption so as not to confuse it with the term "Passphrase" from BIP39 which generates a new wallet using this as a "salt" on top of the seed phrase. OK?
Why is this getting off topic since I suggested a viable and secure alternative of encrypting the file containing the electrum wallet, sparrow etc? Using these as an additional alternative (one thing does not exclude the other, you can opt for both) backup and not only write down 12 readable words that anyone with access to this could see and try to import to steal the funds (if the funds don't are allocated in a hidden wallet generated by the BIP39 passphrase).
Encrypted keystore files you can save digitally and can use them to recover as well while the wallet seed phrase should not be stored digitally.
Keystores are very easy to replicate, facilitating the backup process and saving to pen drives in geographically different and distant locations.
Of course, we must always keep a physical copy of the seed phrase written down on paper, steel plates, etc. As I said, one thing does not exclude the other. However, it varies depending on each person's paranoia, if the person is afraid of having their funds stolen, they can use the BIP-39 passphrase and the method I mentioned in this topic: encrypted backups (in the same way as the wallet backup works bitcoin core, electrum, etc.).