Typescript is relatively new, and I think a lot of those companies are still trying new things and experimenting with what works. I expect that we will see more refined content and books about TS-at-scale in the near future though.
However, for those looking for a great way to learn Typescript from a beginner's perspective I can fully recommend Execute Program[1].
At the speed of javascript though, it's pretty mature now. When I tried searching on Amazon I was getting back $30+ dollar ebooks with chapters on how to use Gulp (superseded by webpack or babel)...
However, for those looking for a great way to learn Typescript from a beginner's perspective I can fully recommend Execute Program[1].
[1]: https://www.executeprogram.com/