If the two points A, B are on a line through the origin, we have a direct proportionality

yA/xA = yB/xB

and the y-axis intercept of this line is q = 0. If the 2 points are not colinear with the origin, i.e., we do not have a direct proportionality, the y-axis intercept tells us the distance we would have to shift the origin and the x-axis up/down to achive the direct proportionality:

(yA - q)/xA = (yB - q)/xB

However, I do not see it as a much of an improvement