Why don't parallel Streams run as fast with Virtual Threads as the common thread pool?

Question

I am experimenting with Virtual Threads in my loom-lab project, and wanted to see if Virtual Threads are faster than Platform Threads when doing a parallel stream, but it actually seems slower.

try (var executorService = Executors.newThreadPerTaskExecutor(virtualThreadFactory)) {
    var candidates3 = LongStream.iterate(3, x -> x < count, x -> x + 2);
    time4 = System.currentTimeMillis();
    var primes3 = executorService.submit(() ->
        candidates3.parallel()
            .filter(candidate -> isPrime(candidate)).toArray()
    ).get();
    time5 = System.currentTimeMillis();
}

where ultimately I get the output (in milliseconds)

sequential time = 7546
parallel   time = 1289
virtual    time = 1388

and in general using Virtual Threads is slower than the common ForkJoinPool. Am I making some basic mistake or misunderstanding somewhere, or has Project Loom not been integrated with Java Streams yet?