parallel task works sequentially about workflow-core HOT 2 OPEN

var taskId = context.PersistenceData;
if(taskId==null){
    taskId = StartLongRunningTask();
    return ExecutionResult.Sleep( 500, taskId);
}
var status = GetLongRunningTaskStatus(taskId);
switch(status) {
	case "OK":
		return ExecutionResult.Next( );
	case "Running":
		return ExecutionResult.Sleep( 500, taskId);
}