My father took me to see a JAL 747 that had suffered an uncontrolled rapid descent enroute to SFO.
The horizontal stabilizers were bent up at a very noticable angle beyond spec.
I'd certainly take issue with the assertion that they were "never perfectly level". Obviously the surfaces are usually tapered, but there are way too many different examples to examine. Example: Horsa glider.
And quite a few have anhedral.