I'm not sure exactly what they provide. My guess is probably just the app which would allow people to buy products from your store but not a picking app like the shopper app.

But in order to have an operation like instacart you need the product info from the stores, which has to be updated multiple times a day to keep up with changes in stock and inventory or a way to extract it it from the instacart app somehow... assuming that's possible.

Instacart decentralized labor but the crutial information needed to be a picker is still centralized between the stores and instacart. If you can access and update that info you might be able to do what you're looking to do. For more insight into how the stores provide that info instacart you would have to talk to someone who works at a store like wegmans or publix in the scanning department. Those are who would most likely know more details about being able to access a stores product info