Sonar Make this member "protected"/ Mutable fields should not be "public static" with Streams

Question

I have added sonar to my project and I am getting Make this member "protected" issue.

I am getting this on a public static final set.

I already have gone through the documents and I know why this is an issue. We can resolve this by using unmodifiable set.

REF: Reference_1 Reference_2

My question is I am getting this issue if I am using streams( Collectors.collectingAndThen(...) or Collectors.toUnmodifiableSet()) to get an unmodifiable set.

Details:

Sonar issue is gone with the below code method of getting UnModifiableList;

Set<String> set = Collectors.toUnmodifiableSet(Stream.of("USA", "UK", "India")
                .collect(Collectors.toSet()));

Issue still present if I am using Collectors.collectingAndThen() or Collectors.toUnmodifiableSet()

Sample Code:

Set<String> set = Stream.of("USA", "UK", "India")
                .collect(Collectors.collectingAndThen(Collectors.toSet(),
                                Collections::unmodifiableSet));

OR

Set<String> set = Stream.of("USA", "UK", "India")
                .collect(Collectors.toUnmodifiableSet());

The codes above will give an UnmodifiableSet so why Sonar is marking this as an issue?