Async bug or not bug. Here is the question.

gistfile1.txt

  ---
  - hosts: localhost
    gather_facts: no
    connection: local
    tasks:
      # This should have finished at worst 13 seconds (+1, poll frequency) after the start
      - shell: "sleep {{ item }}"
        async: 20
        poll: 1
        with_items:
          - 9
          - 7
          - 13
          - 11

PLAY [localhost] ********************************************************************************************************************************************************************

TASK [command] **********************************************************************************************************************************************************************
changed: [localhost] => (item=9) => {"ansible_job_id": "293350696203.30461", "changed": true, "cmd": "sleep 9", "delta": "0:00:09.004775", "end": "2017-05-09 14:15:27.104503", "finished": 1, "item": 9, "rc": 0, "start": "2017-05-09 14:15:18.099728", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}
changed: [localhost] => (item=7) => {"ansible_job_id": "199981395199.30574", "changed": true, "cmd": "sleep 7", "delta": "0:00:07.004524", "end": "2017-05-09 14:15:34.362792", "finished": 1, "item": 7, "rc": 0, "start": "2017-05-09 14:15:27.358268", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}
changed: [localhost] => (item=13) => {"ansible_job_id": "274078183703.30669", "changed": true, "cmd": "sleep 13", "delta": "0:00:13.005118", "end": "2017-05-09 14:15:48.363892", "finished": 1, "item": 13, "rc": 0, "start": "2017-05-09 14:15:35.358774", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}
changed: [localhost] => (item=11) => {"ansible_job_id": "806225950244.30832", "changed": true, "cmd": "sleep 11", "delta": "0:00:11.005086", "end": "2017-05-09 14:16:00.104379", "finished": 1, "item": 11, "rc": 0, "start": "2017-05-09 14:15:49.099293", "stderr": "", "stderr_lines": [], "stdout": "", "stdout_lines": []}

PLAY RECAP **************************************************************************************************************************************************************************
localhost                  : ok=1    changed=1    unreachable=0    failed=0

Have a look at the start time and finish time. They were all running one after each other.
Whatever the strategy is.

I don't know what to expect.