Have you tried dismissing the splash screen in your actual page ionViewWillEnter, within a 100ms setTimeout function, instead of the app.component.ts?
That might do the trick. Otherwise, take a look at my blog post, which also references a thread here. It ‘fixed’ the issue of the splash not being correctly sized and also the white/grey flash for me.
Note: I am manually dismissing the splash screen with a setTimeout of 100ms when ready and I set to the 30000 timeout in the config file)