It doesn't do that. nand_do_upgrade only reformat the partitions if it fails to attach it, and it may successfully attach a UBI partition from leftover data even if the partition offset/size changes. Maybe explicitly format the two partitions if the system is started from initramfs?

Is the removal of the ZTE MF289F intentional?

Just a little nitpick, but, formatting :)

Wonder if this can be dropped by first adding the qca-nss-dp package and then the target Makefile? Seems strange to first add the target that won't actually work as it won't have any ethernet driver and then add the package for it?