https://access.redhat.com/documentation/en/red-hat-jboss-enterprise-application-platform/7.0/paged/configuration-guide/appendix-a-reference-material#undertow-attribute-refs

In Table A.48. file AttributesTable A.48. file Attributes of file Attributes, description of case-sensitive attribute just says "Use case sensitive file handling".

However, case-sensitive="false" will be case insensitive only when the underlying file system is case insensitive. (i.e. case-sensitive="false" will become case insensitive on Windows NTFS / Mac OS HFS+ but this setting does not on Linux ext3/ext4/XFS.) This is not a bug but an expected behavior.

Please add this note on the documentation.