Hi, reading your interesting article, I wonder if the real difference in perceiving linear and non linear motion is, that humans easily can predict the motion path for a non linear motion.
If the brain detects a non linear motion it will predict the motion path from only a view data points.
When it comes to non linear motion the brain needs to observe the entire motion from start to end to make sens of it and will have to check each single data point.
Linear motions don’t let us make any predictions in advance, because they are not natural.
For example if you see somebody kick a food ball your brain will instantaneously predict a trajectory path and roughly estimate where the foot ball will land.
There will be little desire to follow the path from start to end. My guess is humans would predict a target destination, then focus on it and wait for the ball to arrive.
When it comes to linear motion, because it is actually hardly observed in nature, the human brain probably has to check each single step repeatedly, to ensure continues motion is still ongoing.
So if your observation is correct, non linear motion easily maps to natural experience, thus can easily be detected and calculated in advance, feels natural and reduces the cognitive load
Linear motion is something, uncommon in nature, and forces the brain to constant observe it from start to end, meaning you need to keep focused all the time.