In reality there are way more people in and around these cities than the census reports. I have been working in Kyle for the past 2 months and the traffic is congested. The city limits in some of these smaller towns hardly tell the full story, same with Georgetown, TX.
The whole story is the fact that 1,400 people are moving to Texas every day and dispersing throughout the state, hence the reason why so many areas are exploding including mine. NYC is losing population, these are based on % points gained, not whole populations. So yes proportion percentages are what are important here. These areas grew larger by percentages than any other city over 20k.
It's changing Texas for the worst because the majority are fleeing blue states.