Floor zones are not for that, floor zones are in simple terms like a nav mesh for AI, basically theyre supposed to define an area that AI can walk on, primarily for them to walk on other entities.
The one you want is a trigger zone, however in this case it won't help because they only have a limited on the radius so they basically detect anything from the ground to the top of the sky that's in their radius.
The easiest way to do what you want would be to write a new script that can be placed on an entity and does a distance check to display text.
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