You seem to know Houston; alas yes Austin was formerly surrounded by open spaces.

But let's not miss the point of the article. This is a right-ward shift of the supply curve. It means that the economics of building the next unit got cheaper. That's the point.

I've seen a lot of neighborhoods across the USA, and Austin making way for higher-density housing on urban corridors (Lamar) is like, duh, this is more live-able. There are new towers along rail and bus route, townhomes packed in, and behind the tree line it's now possible for some single-family lots to become duplexes or fourplexes. And rather than McMansion ugly, the new Austin residents are dressing those up to look pretty darn cool.

There is a lot more to be done to remove supply-side barriers in every city.