> Windows doesn’t have it at the file system layer, NTFS is case sensitive.

I think the common phrasing is "case-aware, not case-sensitive".

No, NTFS has always been at least optionally case sensitive; current Windows versions even allow case-sensitivity to be controlled on a per-directory basis[1], which even works for (some) Win32 programs:

  Microsoft Windows [Version 10.0.22631.3593]
  (c) Microsoft Corporation. All rights reserved.
  
  C:\Users\jtm>mkdir foo
  
  C:\Users\jtm>fsutil file setCaseSensitiveInfo foo
  Case sensitive attribute on directory C:\Users\jtm\foo is enabled.
  
  C:\Users\jtm>echo bar > foo\bar.txt
  
  C:\Users\jtm>echo Bar > foo\Bar.txt
  
  C:\Users\jtm>dir foo
   Volume in drive C is Aristotle-Win
   Volume Serial Number is E4AE-428B
  
   Directory of C:\Users\jtm\foo
  
  2024-05-31  17:55    <DIR>          .
  2024-05-31  17:55    <DIR>          ..
  2024-05-31  17:55                 6 Bar.txt
  2024-05-31  17:55                 6 bar.txt
                 2 File(s)             12 bytes
                 2 Dir(s)  41,524,133,888 bytes free
  
  C:\Users\jtm>type foo\bar.txt
  bar
  
  C:\Users\jtm>type foo\Bar.txt
  Bar

[1] https://learn.microsoft.com/en-us/windows/wsl/case-sensitivi...

That's way worse than just putting it on the file system.

Now you have hidden information, that you can't ever change, and may or may not impact whatever you are doing.

What hidden information that you can't ever change?

I think what they mean is if you somehow had two files with the same name but different cases (as NTFS supports this) it would be impossible to fix with win32 calls