If it's the same as on Win10 it's a UWP App that needs a ton of dependencies like .net, WinUI2/XAML.
The appx is: Approximate size 21.8 MB according to https://apps.microsoft.com/detail/9wzdncrfhvn5
Win7 calc.exe had 758KB for i686 and 897KB for amd64.
Reminds me of the early days of MacOS X when the Calculator app was written in Java as a demo of how fantastic and native their Java integration with Cocoa bindings was. This of course made it horribly slow to launch since initializing the JVM back then was a massive chore.