I have seen that it's possible to boot from nmve via emmc or ssd.
But i have also done some reading.

Here's my wild guess's.
I looked at Uboot and seen that they seem to think it's possible to boot from nvme The link is to c commmand on U-Boot. https://github.com/u-boot/u-boot/blob/master/cmd/nvme.c

Now i had seen that i made a look to try find any reference to Nvme in rockchips's version of U-Boot and found the following in a file.

#ifdef CONFIG_RK_NVME_BOOT_EN

So in that we use rockships U-Boot and there are several files that refernce U-Boot in some way , i think if we had decent support from the developers here that we couple be one of the bettter boards that can boot from nvme. Either that or we have a good coder that like these boards.

I am no coder , i can only find infomation & able to compile files wuth the right instructions.