Technically, GA Connector doesn’t send any traffic source data to GA.
It only sends information like revenue in combination with GA Client ID, which serves as an identifier of the user.
Google Analytics already knows all users’ traffic sources (including the first click).
With GA Connector, it also knows CRM data about some users (e.g. revenue stats).
GA Client ID serves as a key that combines traffic source and CRM data.
It means that you can use CRM data will all attribution models available in Google Analytics.
You can read more about this here: