Ros install for a git commit iso

I just built an ISO from commit b205985. It built ok, and I was able to boot it was no issues.
I tried doing a ros install to disk (ros install -c -d /dev/sda", and it didn’t have the running image in system-docker images. (rancher/os:b205985) - so it couldn’t save the running image to disk.
Was is supposed to load the running image into system-docker when the ISO boots?
Is installing an intermediate commit to disk a supported thing?

as part of re-doing the installer, I have started adding a cut down version of the installer image to the iso - see

When I’m testing a previous version, I push the installer to some random hub organisation - like zombie/os:b205985) and then specify the installer image on the cmdline ros install -i zombie/os:b205985 -d /dev/vda