It’s not about encryption itself; it’s about using the encrypted seed phrase as a decoy.
If that's the only objective then the solution already exists and there is no reason to re-invent the wheel. It is called the extra word or the passphrase. It is any phrase that you can add to your existing seed phrase to derive an entirely different set of keys. The seed is still the same and is the decoy itself. The only way to access the funds is to know that passphrase.
That passphrase can be the same password you used to encrypt in your algorithm (birthday, passport number, etc...).
Although both involve
data-encryption-secret, they're technically not the same, their structure isn't identical.
BIP39 passwords use 2048 iterations when adding passphrases, but this method increases that to 60 million, making brute-forcing practically impossible.
If I post a BIP39 seed here, no one can determine with certainty whether it's standard, password-protected, or encrypted with this script.
That's what security through obscurity is all about. Hackers follow the usual standard, so if they don't know which path leads to the target, I doubt they'll be able to make progress.
This is how second layers of security should work, in my opinion. It's not just about encryption, but about adding an additional, unpredictable move to confuse potential attackers.