PHP BackedEnum interface fails the instanceof operator

Given:

enum TestEnum: string
{
  case CASE_1 = "first case";
  case CASE_2 = "Second case";
}

This is supposed to return true:

TestEnum::class instanceof BackedEnum

But I get false

I tried the following from this post (it fails to run in Laravel Tinker REPL, but runs as a script?):

interface TestEnumInterface extends BackedEnum
{
    public function foo(): string;
}

enum TestEnum: string implements TestEnumInterface
{
    case CASE_1 = 'case 1';
    case CASE_2 = 'case 2';

    public function foo(): string
    {
        return 'bar';
    }
}



TestEnum::class instanceof BackedEnum //false
TestEnum::class instanceof TestEnumInterface //false

What am I missing?
Running PHP v8.1.13

Thanks

UPDATE:
Indeed, as per SomeOne1 reply, the following returns true:

TestEnum::CASE_1 instanceof BackedEnum

Then I’ll try to be more specific.
I have to test a variable $list which could be a number of different enums (like $list = TestEnum::class or $list = AnotherEnum::class), or a Laravel collection, or an array.

  //if ($list instanceof BackedEnum) {
  if (isset($isEnum)) { // I want to get rid of this
    // do stuff
  }
  else if ($list instanceof IlluminateDatabaseEloquentCollection || $list instanceof IlluminateSupportCollection) {
    // do stuff differently
  }
  else if (is_array($list)) {
    // do stuff differently
  }
  else {
    var_dump($list);
    dd('invalid list');
  }

Then how can I test if this variable is of enum type?