Not an answer, but some related information: Since this has eMMC, it is not a dev kit. It is a separately purchased module with a third party carrier board. Most likely it requires the third party board support package for any kind of flash (which is usually the same as dev kit, but with modified device tree).
SD card models (dev kits) have the SD card slot on the module itself; third party setups with an eMMC module have the SD card on the carrier board, and not on the module. Drivers and device tree differ quite a bit for these, and normally SD card boot is not supported on a third party carrier board without additional work (e.g., it might use an initrd flash).
SD card content on a dev kit is just the rootfs. There are a lot of other partitions, and they will either be found in QSPI memory (on the module; part of a dev kit), or in those other eMMC partitions. Boot content intended to be on an eMMC partition will need to remain there even if you are booting to an SD card rootfs. See this regarding some of the “extra” partitions of an eMMC model:
https://forums.developer.nvidia.com/t/topic/232508/15
Don’t even try to put those extra partitions on an SD card for an eMMC model.