How to set IonicConfig for a specific platform in Ionic 4?

Ionic Framework
1 

import { IonicModule } from 'ionic-angular';

@NgModule({
  ...
  imports: [
    BrowserModule,
    IonicModule.forRoot(MyApp, {
      tabsPlacement: 'bottom',
      platforms: {
        ios: {
          tabsPlacement: 'top',
        }
      }
    }, {}
  )],
  ...
})

This is from the ionic v3 website. Seems like using platforms is not possible in forRoot anymore. How do you do something like this in Ionic 4? I’m trying to set scrollAssist to false on Android and true on iOS as the auto scrolling doesn’t work properly on Android.