Works for me.
Image without tweak set.
Image with tweak set.
As can be seen, 'Test Author' became 'Author, Test'. Both were displayed under 'A', using the author's sort value.
Note that the author's sort value is used when displaying author lists in the tag browser or the content server, not the book's author_sort value. If you want to use the book's value, then itimpi is right, there is no way.