To be clear , you’re suggesting that there’s a map of labels (diapers, cereal etc) to marketing ids so apple can still say they anonymize your data even though for all intent and purposes, they don’t?
It lets them say they never sell your data, but they do sell meta-data about you. Probably a little over simplified but you get the idea.
You don't need to identify the customer.
I did some work with an online supermarket some time ago and I found some interesting associations worth trying like Sliced Brioche Bread + Nutella :-)
Sadly I didn't find any association like 'beer and diapers' ;-)