The PHP remove() method set with safe => true is returning instantly and not outputting any count for the removed docs even though I can see the remove op in db.currentOp()

try
{
$DBMongoConn = new Mongo($config['database']['mongodb']['server']);
}
catch (Exception $e)
{
throw new Exception('MongoDB Error: connection failed: ' . $e->getMessage());
}

$collection = $sdDb->selectCollection('metrics');

try
{
$result = $collection->remove(array('accId' => $account['accountId'], 'tA' => array('$lte' => $deleteTime)), array('safe' => true));
}
catch (Exception $e)
{
die('Query failed (' . _LINE_ . '): ' . $e->getMessage() . "\n");
}

$error = $sdDb->lastError();

—

$account['accountId'] = int
$deleteTime = MongoDate

—

$error['err'] is null
$result['n'] is 0

db.currentOp()

{
"opid" : "shard1:418732718",
"active" : true,
"lockType" : "write",
"waitingForLock" : false,
"secs_running" : 124,
"op" : "remove",
"ns" : "sd.processes",
"query" : {
"accId" : 1,
"tA" :

},
"client" : "10.121.12.228:33739",
"desc" : "conn"
},