Item 3c above makes the assumption that people observing this within a flying club will be aware of the different levels of safety provided for public transport flights compared with private (club) type operation. They are then in a position to assess the risk for themselves and decide whether to fly with you or not.
If you advertise the flight at your work, people observing it may not be aware that a private flight does not enjoy the same level of oversight as a public transport flight and therefore may not be able to make a balanced judgment. That is why you are not allowed to publish details of such flights outside of a flying club. You can invite colleagues by word of mouth.