What the census means by “Urban area” generally boils down to is “the majority of the labor in this area working in a place with more than 50k population”. That is a better metric than “what’s the population of this city/ town/ community” since you can have small towns inside urban areas that are going to feel dramatically different than a small town with no direct connection to a nearby population center, but the small town in podunk Nebraska would have far more in common with a small town in podunk Arkansas than a nearby suburb.