I am not sure I understand the question completely.
But - without testing - it comes to mind, that GetSelectedObject5 return a zero-based array (of selections). So if you only have selected one object (your sheet) you should use Set SwFeat = SwSelMgr.GetSelectedObject5(0) to retrieve it.
SwFeat is Nothing
Set SwFeat = SwSelMgr.GetSelectedObject2(0)→Result is false
the code is
Private Sub ll9()
Dim SwApp As SldWorks.SldWorks, SwModel As ModelDoc2
Set SwApp = Application.SldWorks
Set SwModel = SwApp.ActiveDoc
Dim SwSelMgr As SelectionMgr
Set SwSelMgr = SwModel.SelectionManager
Dim SwFeat As Feature
Set SwFeat = SwSelMgr.GetSelectedObject2(0)