While the default extent in GeoSAFE is now the extent of all valid layers, this can be overridden as part of a custom theme.
At the INGC in Mozambique, all local theme elements are defined in http://github.com/kartoza/ingc_geonode_theme. Among other settings there is a custom default extent, which for the INGC is the extent of the country of Mozambique, no matter what layers are available.
https://github.com/kartoza/geosafe/issues/394