The of transparency suggests they felt the “why” would infuriate you further, so they are withheld details in an attempt to avoid blowback.
Right thing to do is to tell you why, give you options and, if you jump to their conclusion, at least you’re on the same page as the service centre.
Patek might feel most clients would balk at a $6000 case reconstruction, with laser welding, but maybe a light polishing is fine for you, with the laser welding being saved for a later servicing.