Here is a post discussing how to find the base view.
https://forums.autodesk.com/t5/inventor-forum/bug-when-searching-for-drawing-standard-type-views/td-...
It looks to be a tricky one to determine as you need to look at all the views and if it has a parent that means it is the child. So when it gets to the parent nothing is displayed and you can add the label text on this view. However as discussed in the post other views can act like this so filters need to be built in to exclusively determine it is the base view. So that means moving through the drawing checking what views could trip up the rule running successfully so some testing is needed. Obviously you can avoid all this by just placing the labels on all the views but this would get unsightly.
Dim oDrawingView As DrawingView
For Each oDrawingView In ThisApplication.ActiveDocument.ActiveSheet.DrawingViews
'Check if a view has a parent, if not, do this.
If oDrawingView.ParentView() Is Nothing Then
oDrawingView.ShowLabel = True
oDrawingView.Name = "Top parent view"
Else
'oDrawingView.ShowLabel = True
'oDrawingView.Name = "Not top parent view"
End If
Next
If you need help piecing it together post up the rule and go from there.
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Regards
Alan