Yes, Kyrill, that's true,
BUT, the open loop gain and hence the feedback factor is determined by the value of this pot. Make it too high and the fb factor increases, taking the stage outside the Bode/Nyquist stability criteria. Stick to 10-25K, nothing higher or lower, otherwise you need to alter the value of the tiny silver mica at C3, changing sonics, possibly for the worse. Everything balances beautifully as it is; this is a sweet spot in the circuit!
Cheers,
Hugh