Isn't English hard enough to learn without terms like adjectival phrase? We always used the term adjective phrase in school when I was coming along. Adjective phrase is the term I recognize, and this term is simpler. You know exactly what it means, or at least you have a good idea what the term is referring to.
One of the reasons English is one of the the most difficult languages to learn -- and it might be the most difficult -- is because of little things like what to call a phrase that acts like an adjective. Why do we have to make this more complicated than it has to be? Why learn two things when one is all you need?
In case you haven't figured it out. English was never my favorite subject and did well to pass the course my senior year of high school. Fortunately, I had to have only one course of it in college.