I think you're taking the interpretation quite far in your post. I've seen legal department giving approval for a much less strict interpretation - basically on the level of "is this cookie realistically useful for this specific purpose". It would be useful to get some real cases that answer those questions, because on one extreme, "strictly" you don't need any local browser storage at all - the product page can contain a form to print out for a mail order and you can track your cart on paper.