If you build geometry and cancel before it completes creating depth maps, then returning to the build geometry dialog allows you to reuse those depth maps even though they are incomplete, giving you an incomplete or strangely formed model
If the previous step had not even finished loading photos then you can still 'reuse' depth maps that had not even begun being created and no model is made.
Perhaps this is not a bug and maybe even a desired behaviour or undocumented feature
