GET requests to piwik.php do not match visitor logs

In my webserver logs I see successful GET requests to piwik.php but some of those ips do not appear in piwik’s visitor logs.

From what I have been able to discover clients should only make that request if the tracking js has successfully executed and ‘Do not track’ is disabled, but I have not been able to confirm that this means they are tracked by piwik.

So my questions are:
Should clients that send get requests to piwik.php appear in the visitor logs?
If not, in which cases will the client not be counted?