The wiki is still in WIP, to write the android image back to the device follow the exact same steps but instead of putting the ROS img path put the Android one.
And yes that is the repo for rkdeveloptool
I received the files from Mekotronics and they also delivered a PDF with instructions for the Windows tool.
In short you have to load the cfg for the emmc and select the spl and image file.
Update: Don’t forget to select “Write by Address”.