The weather app isn't a native app either:

> According to Windows Latest, the high memory consumption is due to the fact that Weather is not a fully native Windows application. Instead, it is essentially an MSN Weather web app built on Microsoft's WebView2 framework. Task Manager shows multiple Chromium-based subprocesses running simultaneously, which contributes to the unusually high RAM usage.

If you have Edge or Chrome open (or anything else that similarly uses Chromium) then the incremental increase in RAM usage from the Weather app is likely much smaller than the headline 1GB.