only match case-insensitively if the fs is

src/virtualenv/discovery/py_spec.py

@@ -5,6 +5,8 @@
 import os
 import re
 
+from virtualenv.info import fs_is_case_sensitive
+
 PATTERN = re.compile(r"^(?P<impl>[a-zA-Z]+)?(?P<version>[0-9.]+)?(?:-(?P<arch>32|64))?$")
 
 
@@ -82,7 +84,7 @@ def generate_re(self, *, windows: bool) -> re.Pattern:
         # Try matching `direct` first, so the `direct` group is filled when possible.
         return re.compile(
             rf"(?P<impl>{impl})(?P<v>{version}){suffix}$",
-            flags=re.IGNORECASE,
+            flags=re.IGNORECASE if fs_is_case_sensitive() else 0,
         )
 
     @property