where was this?
though they can do that if they want. much like with policies enforcing masks, they can choose to refuse service to any customer for whatever reason. its their store, and they are a private business. it will make for some good karens in the wild videos on youtube of unvaxxed people making a stiink about getting vaxx checked at the grocery store and then getting trespassed.
Although I generally agree with you, i think it’s important to note that, depending on where you live, there are a great many reasons that are in fact not allowed to use to deny entry or services, such as on the grounds of being a member of a protected class.