The site you are referencing has been compared to maps of all Sprint sites. In addition, the key on that site states that it only shows sites upgraded in the last 6 months.
SignalCheck is one word and it's by Blue Line Computing.https://play.google.com/store/apps/details?id=com.blueline.signalcheck&hl=en
Here is the link to the thread for the app too http://s4gru.com/index.php?/topic/3060-signalcheck-android-app-to-monitor-your-2g3g4g-lte-signal-strengths/
At Como Park it is blazing. Downtown St. Paul I only get a faint signal outdoors from a distant tower outside of downtown. In my office in the North Loop of Minneapolis I get LTE. You are right though that it's currently hit or miss in places, but they keep lighting up more towers each week and it's been getting better and better.
You can become a sponsor to this site to get site locations http://s4gru.com/index.php?/topic/1195-information-about-s4gru-sponsorship-levels-and-how-to-become-a-sponsor/
Haha, I had just looked at the map and was like who is the guy always talking about Austin. Yes, backhaul delay is the safe assumption for why 3g and not LTE in Samsung markets.