This extension currently tries to take a screenshot whenever a step fails, even if that step fails because a session can't be started due to a driver failure. This causes the scenario in question to be skipped instead of failing, resulting in false positives.
Sorry for replying so late. Nice catch!
The problem is that the Mink library has changed the behaviour of the Behat\Mink\Mink::getSession() method from this to that, so the session won't start automatically like before.
This extension currently tries to take a screenshot whenever a step fails, even if that step fails because a session can't be started due to a driver failure. This causes the scenario in question to be skipped instead of failing, resulting in false positives.