Stuck in a loop of freeing up space and filling it up again when rebuilding

I still don’t quite understand this. If I’m supposed to upgrade the data conatainer too, why doesn’t it appear in these instructions?

And isn’t the whole point of the two container setup that I don’t have to rebuild the data container? Well, I guess, not, but if someone could help me understand what the proper procedure for a two container setup is when /admin/upgrade/ tells me to do

cd /var/discourse/
git pull
./launcher rebuild app