Thanks @GauravJobanputra! GIS Professional user type, named user license. This may help, after nearly two hours, the Create Mobile Map Package job I started using the gp tool and simplified map, finally errored out:
The error message indicates the details layer datasource cannot be opened yet details are clearly visible in the map:
Our network firewall does drop inactive connections after some period of lack of activity but I think this would just be further indication that the gp tool is not querying the datasource at all. Further, the details layers is included in the MMPK shared using the ribbon tool.