Deer-resistant means deer eat it last. It is a ranking, not a guarantee, and the ranking gets shorter as winter goes on. A deer in February, with the benches grazed down, will eat a long list of things the book says it will not.
Two things make the label less reliable than it looks. New nursery growth is soft and well fed, and it is more palatable than the same plant will be once it has hardened off and spent a few seasons here — so a planting is at its most vulnerable in exactly its first two winters. And pressure varies enormously inside a few miles. A property backing onto open ground, a bench edge or a drainage gets hit in a way a house in the middle of town does not, and the same plant list succeeds on one street and is stripped on the next.
Used properly, the tag is still one of the most valuable filters on a plant list in this valley. It shifts the odds far enough that a planting gets established, and most of it stops being worth a deer's attention once it has.
What it does not replace is protection through those first couple of winters. That is the cheapest insurance on any job where deer are around.