Why on Earth people insist on this? Here is a graph:
x-asis is the year, y-axis number of points.
Except in the fourth year when there was a massive jump, he basically improved over each season with almost the same amount of points.
Year 1 to 2: +5 points
Year 2 to 3: +8 points
Year 3 to 4: +15 points
Year 4 to 5: +5 points (assuming he wins the match this weekend).
That is very close to linear.
Now, see the Arteta vs EtH graph:
Do you see the similarities between them? No, you do not. Because there aren't any.
NB: You get a similar picture in goals scored, goal difference etc.