This table seems to disagree: http://www.demographia.com/db-uscity98.htm . From the totals at the bottom, I found that the average population density for the 600 largest cities in the U.S. in 2000 was (total population)/(total land area) = 99,000,000 / 34,000 = 2911 people per square mile. Kansas City's density is 1100-1400 people per square mile, meaning that not only is it false that it's as "dense as any other developed urban core", but in fact it is not even half as dense as the average city (with population 50,000 or higher).

I think part of that is the way the city is laid out. I think Kansas City is more consistent than most cities in having major roads travelling about every five or six blocks. This probably helps when physically putting the fiber down.