I'll quote your link for documentation purposes only. I'm not promoting the bullshit that is shown in the video. The video creators will try to sell their so-called "cracked Bitcoin-Qt" version. You very likely pay them for some malware or ransomware.

What you're promoting here is likely complete bullshit because even for such an ancient version of Bitcoin Core 0.18.1 (why the heck would such a version be needed?) the encryption and decryption of private keys in a wallet.dat doesn't work like the way the video guys explain in their video description. It's not that you can bypass the entry of the wallet encryption password because this is needed to derive a key to decrypt the secret random encryption key which encrypts all sensitive data in a wallet.dat file like the private keys.

Without the wallet encryption password that the user defined at some point of time, you simply can't decrypt the AES encrypted secret random encryption key (this key is not revealed to a user, it's an internal random secret) and this secret internal encryption key encrypts the private keys of the wallet. (This two-step method allows to change the wallet's encryption password without the need to decrypt and re-encrypt all the private keys in the wallet, it's only needed to re-encrypt this secret internal encryption key.)