Any link you see claiming to offer this is likely one of the following:
To perform a firmware revert, you cannot simply use a USB stick. It requires specific hardware to interface with the console's and NOR chips. Microcontrollers: Teensy 2.0++: The industry standard for dumping and patching Syscon data. TNC (Tiny Jumper Cable) downgrade tool ps4
A popular open-source utility used to validate and patch the console's NOR and Syscon dumps. PS4 Syscon Tools: Any link you see claiming to offer this