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While I can't argue that there are some differences it types, I would have avoided the whole problem altogether if the Object browser didn't show this as the signature for the filter on AcadSelectionSet.Select: (copied and pasted directly from the Object Browser)
Optional ByVal FilterType As Object = Nothing, Optional ByVal FilterData As Object = Nothing
If you use Object, it doesn't work, and while it's a short leap from {color:#0000ff}Integer{color} in VBA to {color:#0000ff}Short{color} in .NET, the leap from Object to Short is a little more obscure.