This confused me as well.
What they are saying is that all cats get the ear clip to show they’ve been vaccinated, if the cat is not going to a forever home and is just being released back into the streets/wild.
Shelters have more intimate knowledge of whether or not the cat is going to be released, so they don’t bother with the tags. Vet clinics don’t usually handle releasing or holding cats and give a rabies tag to cats that they vaccinate because they deal more with owners and pets who could have a reason to put such a tag on a collar.
I agree. Not many cats even use collars. I thought they were the relic of some optimistic veterinary practices lol