Extension only for new Firebase user signups, not existing?

[backrsports]

We successfully connected this extension and it works wonderfully with both sides, however it's only syncing new users of our Firebase attached app, not the roughly ~5k in our current Firestore user collection. I would just batch import on Sendgrid's side, but it looks like there's much-needed meta fields to sync the two through this extension as seen in this screenshot of a successful new user connection.

Thanks!