empty in default action_session_start in Rasa 2.0

When trying to extract metadata from a custom connector request I came across this post: Set slots using request metadata

The code was very helpful and I was able to access the metadata through the default action action_session_start through the tracker.event field.

However when trying to run this code using Rasa 2.0, the tracker.event field will always return [] (an empty array).

My question: Why is tracker.event empty when the code is run in rasa 2.0, and if this is by design how would I access the metadata in the default action action_session_start?