I've noticed that instacart (and by extension, Costco same day shopping) has integrated an LLM into their search. It's awesome to be able to search for "ingredients for a chicken and vegetable roast" and have all the separate ingredients you need be returned. You can also search for things like "healthy snack" or "easy party appetizers".
I think this is a great use case for LLM search since I am able to directly input my intent, and the LLM knows what's in stock at the store I am searching.
Nothing you describe hasn't already been done in the pre-LLM era with simple keyword matching.
In the city i lived in 2012, the (now defunct) local supermarket chain could handle your roasted chicken request. You could also paste an entire grocery list into a text box and have it load the items into your cart all at once. That's the feature i moss the most.
I just tried your snack and appetizers requests with the grocery service i currently use, and it worked fine. No "AI" needed.
I think this is a great use case for LLM search since I am able to directly input my intent, and the LLM knows what's in stock at the store I am searching.