I remember visiting their web page from my phone. I remember visiting the restaurant last Friday. I don’t remember signing up for a newsletter, or actively giving them my email address.
I paid with my credit card by handing it to the server, who returned with the slips for me to sign.
I’m guessing that this is related to a merchant feature of using Square (or whatever they are named now) as a credit card processing platform, along with the fact that often with Square I’ll have email receipts instead of paper receipts.