The selection is directly tied to the JWO technology which almost by definition gets confused by brands whose product line labels (e.g. flavors) are too similar, which is the common case not the exception. Sure, they have the same price but then the breaks automated reordering from the DC. The only solution is to not carry variations of a product, which then leads to crappy selection. Fine for a convenience store not fine for general purpose grocery.
source: I owned a chain of specialty food retailers as well as a warehouse, and this issue even stymied humans at times!
That said, I'll grant that it's also creepy AF. The bigger issue for me, though, is that Amazon is so fucking awful at physical retail inventory management (both the selection of items that should be there and the selection of items actually available for purchase) that the Go Grocery in Seattle went from being "this is how I buy groceries" to "there is zero chance they'll have most, let alone all, of the items on my incredibly boring grocery list."
Amazon still wins, though... I end up walking the other direction and going to Whole Foods...