The 10 ohm speaker terminal lad resistor was dropped some years ago, as it was unnecessary. The 120 ohm resistor remains standard because it's the old IHF (now IEC) standard for headphone circuits. The reason it's standard is that it roughly equalizes the output from a wide variety of headphone impedances from 24 ohms to 600 ohms. Without it, some low impedance 'phones sound better due to better damping of the LF resonance, but they can be very loud. That of course makes the turn-off transient louder as well.
I imagine that a search of the forum would turn up several discussions, since this comes up fairly often. I have proposed an L-pad (fixed or variable) at the output as a suitable way to reduce the sensitivity of low-impedance phones without raising their source impedance.
