union-extends-bug?

[ReneMiner]

What's going on here?

This is a small testscript. As far as i know it should print out 4 times 8...

Uses "console"

Alias Quad As t_DataHandle

Type t_DecodeDataHandle
  pData As DWord
  pType As DWord
End Type
  
Union u_DataHandle
  hndl As t_DataHandle
  my   As t_DecodeDataHandle 
End Union


Type any_Data Extends u_DataHandle
  Be As Function
  Is As Function
End Type  
Function any_Data.Be(ByVal s As String)
  If HEAP_Size(Me.my.pData) Then HEAP_Free(Me.my.pData)
  Me.my.pData = HEAP_AllocByStr(s) 
End Function
Function any_Data.Is() As String  
  Function = HEAP_Get(Me.my.pData)
End Function


PrintL "quad:              " & SizeOf(Quad)      
PrintL "t_DecodeDataHandle " & SizeOf(t_DecodeDataHandle)
PrintL "u_DataHandle       " & SizeOf(u_DataHandle)
PrintL "any_Data           " & SizeOf(any_Data)

'PrintL
'Dim foo As any_Data
'foo.Be("some data")
'PrintL foo.is
  
PrintL " -- key to end --"
WaitKey

now what surprise... the extended type is double the size but has no additional subelements...

but now becomes weird:
goto line 12 that says:

  my   As t_DecodeDataHandle

and remove "my As" so it just says:

  t_DecodeDataHandle

now the union becomes larger but the extended type equals the unions size... strange...