IMX6ULL compiling u-boot for 1GB eMMC device version

In u-boot compile instructions there is special step mentioned for IMX6ULL.

Is is safe to assume that this does not apply to the 1GB eMMC version module of IMX6ULL (PN:00621100)?

You should use colibri-imx6ull-emmc_defconfig when building U_Boot for the 1GB eMMC version. And yes, the Additional Mandatory Steps for Specific SoCs are not required for eMMC version. Please check for details here