Traits and mixins are different. A trait/interface/protocol doesn't generally contain implementation, and when it does, it is based only on other methods in the trait (for things like default implementations), whereas mixins are just fragments of a class implementation with potentially arbitrary dependencies on methods.

So traits document the dependencies that mixins make implicitly.

Traits in typed languages can only cause name clashes if two methods in different traits have the same name and the same type signature. This is immediately obvious, and the compiler will warn you so you can fix it there and then when you try and implement them both for one class. (It also brings into question whether there should be another trait to hold that shared method).

The snowballing complexity that is mentioned stems from all those implicit dependencies: There's no way of knowing what they all could be in a nest of related mixins, whereas the corresponding traits document it and provide a map, of sorts.