This is the new Tow-Boot graphical installer for installing to the SPI flash chip. It has the protective flashing progress that makes sure that there's never an invalid tow-boot image on the SPI flash at the same time as a valid boot signature by first wiping the signature at the start, then flashing tow-boot and after that putting the valid signature back in. This ensure that if a flash fails in the middle it won't be stuck booting SPI and it's easy to recover by booting from SD again. https://tow-boot.org/