From an information theory lens, that makes perfect sense. Proximity to a city is proportional to the incentive and ability to increase information density in a city's name. The closer you are to Toronto, the more often the name comes up, so greater incentive to shorten it. And the closer you are, the more likely people are to know what you're talking about when you say "TRONO" because if there's ambiguities, we usually assume it's the one that's closer.