Why are Google and our website are showing up as a referral? We don't see them in GA.

UTM Stitching

We supplement Shopify UTM data with GA Enchanced Ecomm data using common keys, such as order id, checkout id (which is sent to GA oftentimes). If an order Id hasn’t been generated, order name, among a few other join keys will be used. The end result is that we can typically attribute 20-30% more orders than just using GA Enchanced Ecomm.

Referrals

Referrals is actually pulled from Shopify server side directly, which means Shopify saw the traffic as such from their backend.