And how are they getting that performance? by rendering what you see directly in your line of sight at full resolution, while in your peripheral vision at lower resolution (and usually blurred slightly so its not too noticeable as being blocky).... with eye tracked that moves depending on where you are looking, so you ALWAYS see full resolution in front of your eyes, yes there is slight distortion on the edges of lenses, depending on the lenses used (the lens flaws you entioned, but I was not talking about that, I was talking about resolution), but with FFR only the center of the display is full resolution, the edges are lower resolution, so if you look to the edges its low resolution you have to move your head to bring that back to the center to get full resolution again.
When I said dont look at performance I meant compared to FFR, the only difference is that the Foveation moves with DFR (although as mentioned you can be slightly more aggressive with DFR as you could lower the resolution further in the periphery due to you never looking directly at it). But its the very fact that it moves with your eyes means its much better than FFR as you always get a clear full resolution view (any lens distortion aside, but thats improving all the time) of what you are looking at without having to move your head.