That is correct. However, I still prefer using union types so that I'm not locked in to TypeScript. By using only union types as "enums" and never using enums

That is correct. However, I still prefer using union types so that I'm not locked in to TypeScript. By using only union types as "enums" and never using enums or namespaces, I guarantee that all the TS-specific code I write can be erased and if I ever were to use just JavaScript in the future, I could. Also, I use Babel to transpile TS to ES3.