Well, what would you can it then? It describes what it does (render at different resolution based on whether it's what you'll typically be looking at, but not dynamically based on where you're ACTUALLY looking, which the word "fixed" makes obvious).
That's the whole point. The rendering can't be defined "foveated" if it's not based on the position of the fovea. The fact that you could look at the centre of the image, or that it would be "typical"(and yet most of time the eye wanders around), it's just a coincidence, like a broken clock showing the correct time two times a day. You can do the same thing in a game on regular tv, but nobody would call it "foveated rendering". And the same thing applies to VR (yes, as said, in VR you can move your head to exactly match the centre of screen on what you want to look at, if you want. But in the actual experience, you look at the gaming world mostly moving eyes aroud, not adjusting continuaously the head position - being forced to do so would be stressful).
That border decrease in detail is more akin to VRS or other means of reducing detail where it's LESS LIKELY that you will be looking at. But foveated rendering is not a statistical thing. It's purpose is to render well exactly only the portion of screen that you are looking at, in real time. There's no distinction of Dynamic or Fixed. This last one is just like calling "Virtual Boy" VR just because the name contains the word "virtual" (while it was just a 3d screen viewer to be looked close with googles).
You could call it "concentric rendering", or "fading rendering", or whatever. But what does it has to be with fovea?
Obviously I can understand that if you imagine to play a game keeping your gaze fixed in the centre of the screen, and you progressively reduce rendering detail the farther you go towards the edges of the screen, then you could imagine to call it like that. But that would not be a rendering based on fovea position: it would be the player keeping the fovea on a fixed point.