FFS refers to extracting data when they have the PIN/password to unlock it already. Having an unlocked device doesn't mean you can extract all of the data from it. Their tool requires unlocking, enabling developer options (requires authentication), enabling ADB, authorizing ADB access from their tool and then uses unintended functionality in ADB to extract all of the data. FFS is their baseline capability which generally works everywhere as long as the user doesn't have a device admin app disabling ADB. They could far more easily exploit the OS after unlocking it but those aren't the kinds of exploits done by the Cellebrite Premium tool and would require something else.
BF refers to brute force attacks after they've exploited the devices, which implies also exploiting the secure element on devices providing throttling with one.