For whatever the reason my TT uses the television antenna for the FM radio. So it is directional and works best when pointed at the station. It also works best when the television antenna is raised.
The AM radio band has never worked because there is no outside antenna. You will see many spring loaded whip antennas on TTs, these are used for the AM reception. My TT never had one.
An easy test is to raise your TV antenna, tune in an FM station and see if the signal strength varies when you turn the antenna.
I doubt if the salesman has a clue about these things.