The increased size of you iOS binary could be caused by the plugins you are using since they use different implementation for each platform.
Do you use any custom plugins?
Furthermore, iOS app uses more pictures for its splash screens
so consider checking their size.
The best way for us to investigate your binary size differences will be by reviewing you package. We will also need you to share the client (in-browser, Windows, VS extension) you are using.
If you are willing to provide your binary please open a private ticket
and attach it there.