According to the Wikipedia page for proportionality[1], the values "can also be viewed as a two-variable linear equation with a y-intercept of 0". Direct (as opposed to inverse) proportionality is a type of positive correlation but they are not the same thing. Because we are dealing with probability percentage as a proportion of the company's size either the size is greater than zero and the probability is 100% or both values are zero.

1. https://en.wikipedia.org/wiki/Proportionality_(mathematics)