The restaurant told Apple Maps that it has an app clip and where the restaurant is located. Because you have location permission enabled (prompted during setup) you are within range so Siri is suggesting it may be helpful for you. The gps can’t tell if you’re exactly in the store, above the store, or next to the store.

This method is far less invasive than relying on GPS, WiFi, and Bluetooth tracking to determine if you’re actually in the restaurant.

Your iPhone will learn your habits over time as the Siri recommendations are processed on device and not on Apples servers. You can remove Siri recommendations in widgets by holding down on it and turning the toggle off.

The company isn’t able to pay Apple to market its app to you via Siri suggestions so technically it’s not an advert but understandable that it appears that way!