How can wifi be a star topology when all clients connect to the base station using the same airwaves? If it really were a star topology, it would also not be possible to use aircrack-ng or other tools to gather data for WPA cracking by passive listening -- that can only happen on a shared medium network.
I think the most accurate classification is that wifi emulates a star topology at OSI layer 2 on top of a layer 1 bus topology.
Wifi is in any case not considered a bus network, rather a star topology network.