JSAnyUtilityExtension.isA<JSBoxedDartObject>() returns false positives

[nex3]

JSAnyUtilityExtension.isA<JSBoxedDartObject>() returns true unexpectedly for values that are not boxed objects when compiled to JS (I haven't tested under WASM). This can be reproduced with the following test:

import 'dart:js_interop';

import 'package:test/test.dart';

void main() {
  group("isA()", () {
    test("returns true for a JSBoxedDartObject", () {
      expect(DateTime.now().toJSBox.isA<JSBoxedDartObject>(), isTrue);
    });

    test("returns false for a JSObject", () {
      expect(JSObject().isA<JSBoxedDartObject>(), isFalse);
    });
  });
}

The first test case passes, the second fails. Tested with Dart 3.7.1.