I believe that those events are only for when Nero requires a disc inserted. For example, if you’re program is running and you manually open the drive then I don’t think any event will fire. Only when Nero needs to find information about the media in the drive will it open the drive and shoot off the events.
If its not that, you seem to have a firm idea of how it works, so perhaps you’re not checking the right drive? (if you have multiple burners)