There are two security mechanisms that prevent you from accidental loss or theft of your Bitcoin:
Seed Backup recovery codes
If you lose your computer or wallet file
The Seed Backup allows you to recover your Bitcoin wallets
Your Passphrase allows you to unlock the recovered Bitcoin wallets
Both the Seed Backup and the Passphrase are required to recover a lost wallet. If you lose the Seed Backup OR the Passphrase, you will not be able to recover access to your Bitcoin if you lose your computer.
If someone steals your computer
The password protects unauthorized access to your Wasabi wallet, should it fall into the wrong hands.
If someone steals your computer and your seed backup
They will be able to unlock the device, but they will not have access to your Bitcoin wallets without the Passphrase
If someone steals your Seed Backup recovery codes
They will not be able to recover your Bitcoin wallets without the password.
If someone has access to both your Seed Backup or computer and its Passphrase, they can steal your Bitcoin! DO NOT KEEP A COPY OF THEM IN THE SAME PLACE!