Dan, you are correct that all modern engine lubricants do an acceptable job in an engine. There are other advantages of using a higher quality product, like...lower NOACK, lower frictional coefficient of the base stock, etc.
Amsoil's Signature Series lubricants are extended drain, and do have higher TBN content from the start.
Can you find his UOA and bring it to this thread. That would be great, and the first of hopefully many additions to the excel spreadsheet.
2014 Mustang GT custom ordered to replace the GT500: Sterling Gray, NAV, Recaros, Brembos, Glass Roof, back up camera, 6 speed auto, loaded
2012 Focus Titanium - 18" wheels with handling package
2009 GT500 Shelby (700 rwhp) - sold