The new Mini 2018 comes with a T2 chip inside. This chip encrypts your SSD to keep your Mac secure. While the T2 is amazing at what it does, it can cause a lot of trouble too if something goes wrong!
If something goes wrong with the macOS installation and you try to use the recovery to re-install macOS the T2 chip will ask for the macOS admin password. Depending on how badly corrupted the OS is, it might not be able to authenticate you and will prevent you from re-installing the OS requiring you to schedule an appointment with Apple Genius Bar.
This becomes a major issue especially for those who like wiping their drives before doing a re-install because the T2 chip would have no admin user to use for authentication.
Having a firmware password means the T2 chip will only ask for this password regardless of the status of the current macOS installation if you ever decide to re-install macOS.
Just remember to keep it written in a place safe because if lost, you will never be able to access any other OS or do re-installs again unless you visit Apple Store or an authorized service center with a purchase receipt for them to reset it for you.
More info on how to enable/disable firmware password here. https://support.apple.com/en-us/HT204455
If something goes wrong with the macOS installation and you try to use the recovery to re-install macOS the T2 chip will ask for the macOS admin password. Depending on how badly corrupted the OS is, it might not be able to authenticate you and will prevent you from re-installing the OS requiring you to schedule an appointment with Apple Genius Bar.
This becomes a major issue especially for those who like wiping their drives before doing a re-install because the T2 chip would have no admin user to use for authentication.
Having a firmware password means the T2 chip will only ask for this password regardless of the status of the current macOS installation if you ever decide to re-install macOS.
Just remember to keep it written in a place safe because if lost, you will never be able to access any other OS or do re-installs again unless you visit Apple Store or an authorized service center with a purchase receipt for them to reset it for you.
More info on how to enable/disable firmware password here. https://support.apple.com/en-us/HT204455