Hi @Anonymous ,
This issue is already raised to the development team.
https://forums.autodesk.com/t5/revit-api-forum/load-as-group-revit-api/td-p/6408
and I think the below link will help you to solve your issue
https://boostyourbim.wordpress.com/2016/07/16/rtcna2016-wish-granted-load-group-from-rvt/