i think this is quite tricky to achieve, the cordova splashscreen activity is started with the navigation bar loaded, so the "resolution" for the rest is not the same as when your actual projects is loaded afterwards.
If you would create an app with navigation bar and status bar always shown it would be easy since then it would be the same.
I can also give you a hint that regardess of the size you have on your splash it will be exported as a centered 1920x1920
The best thing is to have the splash totally different than the game, or if you have a "lightweight" project you can remove the splashcsreen plugin totally and let the app load directly into the project.