deleting test Facebook users - open graph still reports users

Question

I saw there was a limit of 500 test users per application, so I figured I would write some code to delete them all periodically. (I create a new test user per automated test)

What I've found is that facebook still reports the existence of the test user even after I delete it. Sample request/response is below. Am I deleting them wrong? Or, is it not possible to really delete the test users and avoid hitting the 500 user cap?

Here is a trace where I query existing users, delete one, and query again. The same user is still in the result:

Request: GET https://graph.facebook.com/220266841382535/accounts/test-users?access_token=<removed>
Response:
{
  "data": [
    {
      "id": "100003291443080",
      "access_token": "<removed>",
      "login_url": "https:\/\/www.facebook.com\/platform\/test_account_login.php?user_id=<removed>"
    },
    ...
  ],
  "paging": {
    "next": "https:\/\/graph.facebook.com\/220266841382535\/accounts\/test-users?access_token=<removed>&limit=50&offset=50&__after_id=100003245483203"
  }
}

Request: DELETE https://graph.facebook.com/100003291443080?access_token=<removed>
Response:
true


Request: GET https://graph.facebook.com/220266841382535/accounts/test-users?access_token=<removed>
Response:
{
  "data": [
    {
      "id": "100003291443080",
      "access_token": "<removed>",
      "login_url": "https:\/\/www.facebook.com\/platform\/test_account_login.php?user_id=<removed>"
    },
    ....
  ],
  "paging": {
    "next": "https:\/\/graph.facebook.com\/220266841382535\/accounts\/test-users?access_token=<removed>&limit=50&offset=50&__after_id=100003245483203"
  }
}