I found that b2evolution expects hits to come from a non-secure site (ie address begining with "http://"). So "https://" address don't show up properly in the referers list.

My bug fix (working for realease v. 0.9.1): in b2evocore/_functions_hitlog.php, function log_hit()
l.43 becomes:
$fullCurrentURL = $_SERVER['SERVER_NAME']. $ReqURI;
l.177 becomes:
$baseDomain = preg_replace("/http:\/\//i", "", $ref);
$baseDomain = preg_replace("/https:\/\//i", "", $baseDomain);