# Does π values vary in Hansch-Fujita equations for a given substituent?

I was reading about Hansch-Fujita equations from Hansch-Fujita paramaters and observed that the $$π$$ values of substituents (analogous to Hammet $$σ$$ values) change according to the specific environment as depicted in the following table:

I can't understand why is that the case. I mean in Hammet equations the value of $$σ$$ for a substituent doesn't vary when changing the environment and what varies is the $$ρ$$ which is a constant specific for each reaction according to Hammet Equation. That is in Hammet equation we have:

$$\log{\frac{K_i}{K}}=ρ\cdotσ$$

But Hansch-Fujita define $$π$$ (the analogous of $$σ$$) as:

$$π=\log{K_Χ}-\log{K_Η}$$

So does they have "include" the $$ρ$$ constant in the value of $$π$$?