So the issue is the following: If you still have a working OS on the NVMe, but need to reflash because of an error like DHCP or something that will not allow you to use that old OLD, when you reflash, the new fresh OS is written to the MMC however, your NVMe still holds an

boot.scr

file in the /boot or /boot/firmware location. Because this file is present, the boot order will still force the NVMe to load while a fresh OS is waiting on the MMC.