Not rocket science here, I suspect this is only not already done as a matter of time/resources! Hoping this request may help.
At the moment the react-native-mparticle only has a method to synchronously get attributions from the likes of Branch, Adjust , etc. This is obviously tricky as on one hand we don't want to call this too early, as in that case there will be no attribution to fetch and it will ultimately not be logged when/if it does arrive. However if we put this call later on in our onboarding flow, the user may quit the app before the attribution is recorded.
In order to be able to log the attribution as soon as it is available, it would be great to have the onAttributionComplete callbacks at the native layer raise an event on the JS layer, that we can subscribe to, and deliver the necessary payload with attribution data.