I don't know what is different in what is placed from content center and what is done with frame generator, but I know that both have properties added to the files. it would be my guess that some value is not the same in this but the code for how I find it can be done can be found something like this..
{code}
Public Sub G_GetPropertiesNames(ByVal oDoc As Inventor.Document)
On Error Resume Next
Dim oProperties As Inventor.PropertySets = oDoc.PropertySets
For Each P As Inventor.PropertySet In oProperties
Form1.ListBox1.Items.Add(P.Name)
For Each I As Inventor.Property In P
Form1.ListBox1.Items.Add(Space(12) & I.Name)
Form1.ListBox1.Items.Add(Space(24) & I.Value)
Next
Next
End Sub
{code}
see attached image of above code
I know that parts placed from frame generator will have Attributes set in them named "com.autodesk.FG*"
I hope that this helps to find your answer.
Mike