Putting aside the fact that it is horribly bloated. Accurately measuring RAM usage is tricky, there are several measurements, and no "right" one. It is clear from the article that what eats up so much RAM is not the weather app itself but the framework it runs on. There is a "Renderer", a "GPU Process",... eating most of it. The thing that the task manager doesn't tell you is whether or not these are shared component…
Got a bit confused by this, because nowhere in the article are the words "Renderer" or "GPU". Regardless - all processes that comprise the app are the app, not just the parent process.
When I run it locally and check in procexp it has 8 webview subprocesses and all together it's using similar if not higher levels of memory than claimed in the article. Private Bytes is over a GB in total. I expect the webview processes are sharing memory for DLLs though.