We require that you use separate app keys for each platform, due to differences in how the iOS and Android platforms work. For example, Google and Apple both require individual push certificates, and the Localytics system tracks those certificates at the app level.
If you use the same app key for multiple platforms, the integration will break in sometimes subtle ways. You will inconsistently receive push messages, if at all, for example.
While the Analytics portion of Localytics may function correctly using the same app key for multiple platforms, push messaging and attribution will not, due to the fact that the push capabilities are very different on each platform and our backend handles this functionality in a very different way.