Yes, although the benefit of a strictly AR device would be that since it takes less processing power, it would be a smaller, thinner and lighter (and less expensive) device. So there are trade offs for both.

If I understand correctly, MR means the headset is capable VR, and then there’s passthrough capabikity which essentially feeds your headset a video image of the “outside world” and overlays info/images on that real world image. AR I believe there’s no “video” that’s being shown. It’s just the outside world being shown through a lens like on on your phone with images overlayed on top of it.