CollectionConverters总是返回原始源对象吗?

CollectionConverts API states

在所有情况下,从源类型转换为目标类型再转换回   再次将返回原始源对象。

This does not seem to be always true. For example, in the following case it is indeed true

val orig = ListBuffer(1,2,3)
assert(orig.asJava.asScala eq orig)   // OK

however here the assertion fails

val orig = ListBuffer(1,2,3).asJava
assert(orig.asScala.asJava eq orig)   // Boom!

后一种情况是否意味着已复制?如果是这样,那么何时复制副本的确切规则是什么?