The anti-pattern described as Deref Polymorphism is not the same as using Deref with the newtype pattern, in order to allow using the wrapped type transparently. In the latter case, the Target type of the Deref trait is always going to be perfectly clear. In case of the antipattern described on the linked page, it is not perfectly clear what the Target type is going to be.

In short, a Deref impl for some type T signals that T represents some level of indirection, and following/dereferencing that indirection can always be done in an unsurprising and trivial manner.