Square app privacy?

Just purchased a corn from the boys scouts in front of Stater Bros, and receive a receipt from Stater Bros! How do they get my email and cross referenced my card/pos/email?

Square automatically sends receipts to the email address you used at any Square seller.

https://squareup.com/help/us/en/article/5212#how-can-i-unsubscribe-from-automatic-receipts