On page https://msdn.microsoft.com/en-us/library/mt260859.aspx the definition of Excel.Workbook has 2 parameters. In the code generated by PowerBI the function has a third parameter. More specifically, the second is always "null'", the third one is "true".
As a test I removed the "null" second parameter and now the tables loaded with the first line promoted as header, exactly as the second parameter is supposed to do.
What happened here? Does PowerBI generate incorrect code or is the definition page wrong or ?
Thanks in advance for your answer