Word does consider nested tables to be tables, the problem is just that the nested tables are contained inside other tables. For instance, to get to the first level of nesting
Code:
Sub TestTables()
Dim aTbl As Table, aTblN As Table
For Each aTbl In ActiveDocument.Tables
Debug.Print aTbl.NestingLevel
For Each aTblN In aTbl.Tables
Debug.Print aTbl.NestingLevel, aTblN.NestingLevel
Next aTblN
Next aTbl
End Sub
The next trick is to come up with a recursive function so that you can drill into deeper nesting levels. This thread
vba - Find/Count all tables in the document's body (including all nested tables of all levels) - Stack Overflow has more inspiration for you.