"2.4 Default Case Conversion" is described as retracted, and it implies there could be various implementations:
Some implementations may choose to have a mixed solution, where they do full case matching on literals such as "Strauß", but simple case folding on character classes such as [ß].
I wonder how ignoresCase(_:) in this pitch is expected to work.
Would it be locale-independent?
Would it take some options, for example, to choose full case folding or simple case folding?