sensor - How does 3-wire RTD or resistance measurement works in bridge of wheatstone?

I cannot understand how 3-wire measurement will improve the resistance measurement.

They say that IF lead resistance $ R_L $ is the same, it will compensate. How can this happen?

If bridge is balanced (without $ R_L $): $ \frac {R_1}{R_2} = \frac {R_g}{R_3} $

If $ R_L $ is added: $ \frac {R1}{R2}= \frac {R_g+R_L}{R_3+R_L} $

$ \frac {R_g}{R_3} $ is not same as $ \frac {R_g+R_L}{R_3+R_L}$; is this true only if $ R_G=R_3 $ in the beginning? So this means that $R_L$ does not get compensated?