I think they're conflating/confusing a bunch of different things here. E-ink tags let stores run sales more often, offer "happy hour" time of day discounts, etc. It's not so much individualized (other than probably some demographic targeting, like raising prices 5-6 pm when well employed people are picking stuff up on the way home).

The personalized pricing is usually by having everyone pay through an app. The app knows your buying history and tracks everything you do so they can fine tune their deals for you, surfacing discounts on things that pull you into the store, running e-coupons when it knows you're price conscious, etc. etc.

Both systems are fair on the surface but exploit the asymmetry of billion dollar information systems vs the average consumer. All of these tweaks ensure they get the maximum amount of money that they can out of their customer base which means on average everyone ends up paying more, all while being very hard to point to exactly how you got screwed.