Youtube Data API Search: list return unrealiable result?

Question

For instance,

//php code
  $client = new Google_Client();
  $client->setDeveloperKey($DEVELOPER_KEY);
  $youtube = new Google_Service_YouTube($client);
  $searchResponse = $youtube->search->listSearch('id', array(
    'part' => "snippet",
    'type' => "channel",
    'maxResults' => "50",
    'order' => "viewCount",
    'publishedAfter' => "2021-10-25T00:00:00Z",
    'publishedBefore' => "2021-10-25T23:59:59Z",
    'regionCode' => "JP",
));

This query return only 9 channels (and the regionCode of several channels are not JP). There should be more than 9 channels under this filter because channel id such as UCUJNWCiqMT_UudVRSSGZ3SA satisfy all conditions (proved by the information return by Channels API) but was not contained in those 9 channels. I have tried to add condition 'safeSearch' => "none", but it doesn't work either.

This is just an example to show that Youtube Data API Search: list seems only return a small piece of data (at least in the case of channels) which were unrealiable.

Was my code wrong or this API does only provide incomplete results? How could I get realiable results?

Best regards