Kotlin parallelStream()和asSequence().asStream().parallel()之间的区别

使用kotlin 1.6.10，似乎parallelStream()和asSequence().asStream().parallel()的行为不一样.后者似乎并不平行.下面是一个示例代码片段，演示了这个问题:

import java.util.stream.Collectors.toList
import kotlin.streams.asStream
import java.util.Calendar

fun main() {
    println("Available processors: ${Runtime.getRuntime().availableProcessors()}")

    val numbers = (10 downTo 0).toList()
    
    println("Using parallelStream:")
    val start1=System.currentTimeMillis()
    numbers.parallelStream().map { println("${it} - ${Thread.currentThread().getId()}"); Thread.sleep(100); it }.collect(toList<Int>())
    println("Execution time: ${System.currentTimeMillis()-start1}")
    
    println("Using asSequence().asStream().parallel():")
    val start2=System.currentTimeMillis()
    numbers.asSequence().asStream().parallel().map { println("${it} - ${Thread.currentThread().getId()}"); Thread.sleep(100); it }.collect(toList<Int>())
    println("Execution time: ${System.currentTimeMillis()-start2}")
}

你可以在Kotlin playground 执行:https://pl.kotl.in/z3sxKHKvL

输出是

Available processors: 2
Using parallelStream:
4 - 1
8 - 10
3 - 1
7 - 10
5 - 1
6 - 10
1 - 1
10 - 10
0 - 1
9 - 10
2 - 1
Execution time: 617
Using asSequence().asStream().parallel():
10 - 1
9 - 1
8 - 1
7 - 1
6 - 1
5 - 1
4 - 1
3 - 1
2 - 1
1 - 1
0 - 1
Execution time: 1105

我不明白这种行为差异的原因.