Yes, as shipped from the factory, the default "root" file system is 
still case-insensitive but the user can change that.  There there are 
file systems on attached disk images and NFS-mounted file systems, etc 
etc.  More to the point, it's not a system attribute, rather it's a 
file-system attribute and, since a file system mount point can be almost 
anywhere in a directory structure, in general, you can't predict where 
you're going to encounter insensitive vs -sensitive behavior; it could 
vary from directory to directory.  But isn't dealing with case-
insensitive behavior just a special case of the general case of what 
extract/extractall do about overwriting existing files?  I don't see 
that addressed in the current docs.