It's been a while since I coded in bash but I'll take a look.
I see the necessary line in the motd is taken from
/etc/armbian-image-release
and then these values are over-written from
/etc/armbian-release
The variable in question is BOARD_NAME.
I guess it would be a simple matter to rewrite BOARD_NAME=..., I just wouldn't know if this had a knock-on effect down the line somewhere.
Having said all this, this is all just cosmetic, the important change will be to /boot/armbianEnv.txt where the line board_name= needs to change, this is what sets the correct dtb in boot.ini.
But it strikes me that even if I send a pull request, that will take someone's time, and if you can't support an hour, maybe the pull request is not worth it?