I am however surprised that 10MB is Swift language runtime - with ABI compat this is supposed to be shared, and that the weather daemon is >6MB (surely this is just a simple API client?!).
I've not done a lot of Swift/iOS/macOS, but I have a passing familiarity. These numbers are basically what I'd expect for a normal app. In other words I think the relative optimisation comes from the fundamentally better technology choice rather than from being particularly careful about performance.