I think this is true in the abstract, obviously the people at the checkout are part of the experience of the store, but they're also completely separate from that entity. When I reflect on the cashier at my local store, I don't think of their specific behavior as reflecting on the entire brand. If the cashier messes up the readout of the total, I don't understand that as my local supermarket making a mistake but rather as a specific mistake of a specific person.

That separation disappears if we put the brand up as a facade and don't interact with the person underneath, like we don't with brand accounts on twitter.