All the archived stats are always null

I think I see why just logging for now and will come back with a fix.

This line looks like it's always going to return a truthy value because it should be singleValueQuery not executeQuery: https://lab.civicrm.org/extensions/archivemailing/-/blob/499379e5b1fbc20e36a38e2fe2338e5ea126b006/CRM/Archivemailing/BAO/MailingArchiveStat.php#L25

$is_archived = CRM_Core_DAO::executeQuery('SELECT is_archived FROM civicrm_mailing WHERE id = %1', [

Then further, where it gets used is always also going to be true because it references $report before it gets assigned.

https://lab.civicrm.org/extensions/archivemailing/-/blob/499379e5b1fbc20e36a38e2fe2338e5ea126b006/CRM/Archivemailing/BAO/MailingArchiveStat.php#L29

if ($is_archived && empty($report['event_totals']['delivered'])) {