If it eases your mind any the 6.2 and 6.5 GM diesels are NOT Detroit Diesels.
You can blame GM directly for them and leave Detroit out of it.
I've got a whole bunch of Detroit Diesel literature, manuals, spec sheets, advertisements, data books.. and so on, a few shelves on the book case full. And not once in all of that is a 6.2 or a 6.5 General Motors diesel mentioned.
Grigg