I've never understood how a station can have a transmitter in one site yet bill it from another city entirely(WGTZ is one that springs to mind as it is in Bellbrook but billed from Eaton, and WDHT is billed from Urbana but the stick is in Springfield). I've always found this kind of silly. The legal ID should have to come from where the tower is located, not wherever the owners want to bill the station from. How this drives me insane...
Stations would (almost always) rather bill themselves as in the largest city in their coverage area -- WGTZ and WDHT would both rather bill themselves as Dayton stations. (indeed, WGTZ at least at one time had a rather famous ID trying, with considerable success, to bury the "Eaton" part of the announcement)
Anyway, WDHT doesn't ID as Urbana because it wants to. If it were their choice, they'd announce "WDHT, Dayton". The FCC requires them to announce as Urbana.
Eaton is the "principal community", as far as the FCC is concerned. (probably better known as "city of license", but "principal community" is the terminology in the rules) The FCC regards WGTZ as obligated to serve Eaton; any coverage they have in Springfield, Bellbrook, Dayton, Beavercreek, Kettering, or anywhere else is incidential. At one time, a station was required to provide programming specifically addressing the needs and issues of this principal community. It was required to maintain a main studio in that community. It was required to maintain a public file in that community.
The 92.9 frequency was reserved for use in Eaton; the FCC -- and the people (or at least, the advertising local businesses...) of Eaton expected the frequency to be used to serve the needs of Eaton. Not Dayton, or any other community.
Often, it made sense to locate the transmitter outside the city limits of this principal community. AM transmitters usually require at least an acre of land, often quite a bit more if directional antennas are required. AM towers are a LOT more efficient on land with high conductivity -- which is often found in/near swamps -- which cities often are not interested in annexing, i.e. they often lie just outside the city limits... FM towers also require a fair amount of land, and neighbors will often fight them as "ugly". There are fewer neighbors outside the city limits. To alleviate interference, FM towers must also be at least some minimum distance from the towers of other stations on the same or nearby frequencies. This might require an Eaton station's tower to be located outside the city limits.
Point being, it was often VERY helpful if not absolutely obligatory for a station's tower to be located outside the principal community it was required by the FCC to serve -- and to announce in its ID.
Many of the rules have long since been repealed. The one requiring a station to identify with the principal community on its license is still on the books. So is a policy prohibiting the deletion of a community's only frequency. WDHT, for example, could not change its principal community to Springfield, because that would cost Urbana its only frequency assignment. (among other reasons)
Lengthy point being, there is a reason WGTZ IDs as Eaton, not Bellbrook.