Mobile Insight Overview shows both cold and warm app start data for RN.
Example from Demo App

Mobile Vitals don't show cold nor warm app start data.

The issue seems to be in the way we query the data. As the RN SDK uses Warm App Start or Cold App Start and the native SDKs use Warm Start or Cold Start.
RN will align with the native SDK in the next major (pr). But to support current and older versions we need to fix the query.