Why RealmSwift SDK for watchOS is taking 42 MB but for iOS it is just 14 MB?

Recently I have added offline saving support to my watch app using RealmSwift. But while uploading the app to TestFlight, It gave me an error

ITMS-90389: Size limit exceeded - The size of the watchOS variant at “/Payload/MyApp.app/Watch/MyWatchKit.app” is 96MB, which exceeds the maximum allowable size of 75MB after app thinning. For details about reducing your app’s size, view: Reducing your app’s size | Apple Developer Documentation

On further investigation I found that Realm + RealmSwift SDK for watch OS took 42 MB (31.5 MB + 10.5 MB),
But Realm + RealmSwift SDK for iOS took only 14.7 MB (11 MB + 3.7 MB), refer to the screenshot below for comparison :-

Due to this, my watch app size is going beyond the allowable size limit, i.e. 75 MB.

However, when I go through the documentation of Realm, I found that

App Download File Size

Realm should only add around 5 to 8 MB to your app’s download size. The releases we distribute are significantly larger because they include support for the iOS, watchOS and tvOS simulators, some debug symbols, and bitcode, all of which are stripped by the App Store automatically when apps are downloaded.

Then why it is taking too much size?
Please help me optimise the RealmSwift SDK size for watch app.

PS: I have installed RealmSwift for iOS and WatchOS using Cocoapods.