This is not the boot sequence of u-boot bootloader! This is the boot sequence of the board SoC.
SPI
eMMC
MicroSD
USB OTG
Please note that if you flash a partial or bad SPI image, the device might get bricked until the SPI is re-flashed. Since it is the first boot priority, you may have to short one of the SPI data pins with ground in order for the SoC bootloader to skip SPI.