The dection networks are known to be speed dependent and the visualisation seems to be similar.
When you're doing about 30 it shows nearly every car in both directions, but on faster, wider roads you see less. I wondered if it might be to stop destructing grey boxes whizzing past in your periphery(?)
Re performance in NoA, the detection range has definitely increased but it's nosier. I've had more phantom lane change suggestions, but it is now able to suggest a lane change before having to slow down for the car in front.