Yes

If you have a fresh board from JLC (i.e. not bought on the openinverter shop) you need to flash the bootloader (stm32_loader.hex) and the firmware (stm32_sine.hex) or foc.hex.
The boot updater is like a small firmware with the sole purpose of updating the bootloader via UART / wifi module. It is intended for people who do not have a programmer like ST-Link. Since the boot loader rarely receives updates, the boot updater is only needed rarely as well.