sorry for the delay in answering, it's been some crazy months lately.Our app has an initialization step that can take a while depending on the device, the network connection and the status of the app. Sometimes the default splash screen time wasn't enough, so we created our HTML splash screen to be displayed in that case. We increased the splash screen time so this second splash isn't seen, but in some cases and devices it's still seen.
This second splash is called the "init page" and you can find it in: src/core/login/pages/init.
After modifying the config.json file you need to run gulp so changes are applied.
Also, remember to compile the app after doing any change in the app's files. Here are some of the commands that compile the app:
ionic cordova run android
ionic cordova build ios