I don't know about the air 3 and 4, but even just the following iPad after the air 2, the pro 9.7, was much less reflective than the air 2, which in turn was less reflective than the air 1.
As mentioned, less reflectivity does not mean less fingerprints in my experience, so the main reason why I put a matte protector in all my iPad is fingerprints. The thing with screen protector is that if you pick the wrong brand it's going to impact the screen quality, but if you pick a good brand it's going to be as good as without, less the reflections and fingerprints (and the hyped brands like paperlike are not necessarily the best in this regard...)