Note:

• The problem occurs if the the array elements are invisibly [psobject]-wrapped, as happens when you create an array via a Write-Output call, for instance.

• As such, it is another manifestation of Objects are situationally invisibly [psobject]-wrapped, sometimes causing unexpected behavior. #5579.

Array.Sort() is just one manifestation: any .NET method call with an array / object[]-typed array argument that relies on seeing the true array element types rather than their incidental [psobject] wrappers will behave unexpectedly from the user's perspective.

Steps to reproduce

# OK, with array constructed *by an expression*.
$a = "b", "ä", "a"; [Array]::Sort($a, [StringComparer]::Ordinal)
$a -join ' ' | Should -Be "a b ä"  # OK - non-ASCII character ä comes LAST in ordinal sorting.

# !! BROKEN, with array constructed via Write-Output, resulting in
# !! individually [psobject]-wrapped strings.
$a = Write-Output "b", "ä", "a"; [Array]::Sort($a, [StringComparer]::Ordinal)
$a -join ' ' | Should -Be "a b ä"  # !! BROKEN - outputs "a ä b" instead

Expected behavior

Both tests should succeed, as it shouldn't matter how the array is constructed.

Actual behavior

The 2nd test fails:

Expected strings to be the same, but they were different. String lengths are both 5. Strings differ at index 2. 
Expected: 'a b ä' But was:  'a ä b'

That is, the string-comparer argument was effectively ignored, because the .Sort() method saw psobject instances, not strings.

Environment data

PowerShell Core 7.2.0-preview.3