Where did the idea that the Keys are a small side area come from

It is repeated constantly and I cannot find the origin of it. The Keys are listed as one of six named regions, on equal footing with the city and the national park.

My suspicion is that people are pattern matching to real geography, where the Florida Keys are a thin chain, and assuming thin means small. But a thin chain with water traversal between every island is not a small area to build or to play in.

Is there an actual source for the small side area framing or has everyone been repeating each other?