Question.
What is the difference between an unpaid advertiser SP posting (advertising) that she is going to visit city X, or an SP asking a pooner to post (advertise) that she is going to visit city X?
Answer: None.
It doesn't matter if it is the SP doing the unpaid advertising or her asking a pooner to do the unpaid advertising for her; or better yet, an SP pretending to be a pooner and then doing the unpaid advertising (and don't pretend that it doesn't happen).
If an SP wants to advertise a tour, then let her become a paid advertiser. If a pooner repeatedly does unpaid advertising for an SP he can be banned as easily as the SP.